synthc

For PvP, the big problem really is the lack of transparency with regard to how the card generates power (and how much power it generates).  I pretty much agree with everything Hirooo said here and I think that removing looter is an acceptable interim change while the ultimate goal should be to rework the ability so that it moves power from void rather than generating free power.
I would suggest a slight buff in the meantime (5-10 power cost reduction or a slight stat boost), because I don't think that Thugs will be very useful if looter is removed.  They saw very little use before looter was buffed, and that's not because people didn't try to use them.  They would still be helpful (though far from essential) in fire mirrors, but not worth it vs shadow any more (still nice to have, but not worth the deck slot), I think; so they would only see use in a very fire-heavy meta.
Your idea #3 may actually be a very good compromise for retaining the unit's usefulness in PvE, though I think it would need a slight buff to still be good in PvP (like cost reduction to 55 power) due to the greatly increased amount of micro needed to get use out of the ability with this change.  That said, I still think that reworking the ability to move power from the void is the ideal solution.  Your other suggestions don't really solve the PvP problems, though.  Waiting until Kubik figures out how to change abilities is pretty reasonable too; I don't think that the card is quite problematic enough to warrant immediate changes.

Totally agree here.  I talked about this and made some suggestions primarily from a returning player's perspective here: 
I think that the solution is to have four main quest-lines that are available from the start - one for each color.  These quests would give account bound R and UR rewards for playing each color.
A simplified example of rewards progression (in no particular order):
Path of Fire:
Firedancer Wildfire Juggernaut Batariel Cluster Explosion (Repeat rewards up to 4 times for charges) High level reward for like 1000 pure fire matches would be promo Juggernaut. Path of Nature:
Spikeroot Parasite Swarm Shrine of Memory Mind Control Forest Elder (Repeat rewards up to 4 times for charges) High level reward for like 1000 pure nature matches would be promo Swamp Drake or Razorleaf. Path of Shadow:
Shadow Mage Nether Warp (B) Harvester Soulshatter Grim Bahir/Shadow Worm (Repeat rewards up to 4 times for charges) High level reward for like 1000 pure shadow matches would be promo Harvester. Path of Frost:
War Eagle Area Ice Shield Northstar (B) Dreadnought Worldbreaker Gun (Repeat rewards up to 4 times for charges) High level reward for like 1000 pure frost matches would be promo Lyrish Knight or Construct. It's important to give players ways to get pure cards early on, otherwise the meta will be completely dominated by splash decks which require fewer R/UR cards.  I also like the idea of allowing players to choose which cards they get as rewards.  As Eirias pointed out, getting some of these more rare, unique, and interesting cards will help a lot with new player retention.
This would devalue these rares and ultra-rares, but that's really not a problem since we're not trying to make money off of boosters.  Effectively making these earnable basic cards opens up the possibility of playing pure decks early, which otherwise just wouldn't happen until people farmed up a lot of BFP to buy these cards.
The requirements for these main questlines should be diverse and require players to play a variety of games modes (it would make sense to require people to play PvP to get the PvP cards and PvE for the PvE cards).
The game has a lot to offer, and now that it's not pay to win we can give new players some of the many cool cards early on, rather than locking them behind a deprecated paywall.

Spikeroot really is essential for pure nature to survive against this (and many other M unit threats).  Oink the mages and then deal massive damage to them with spikeroot.  Parasite (the spell) also helps since it has high single target DPS and can jump to up to 6 mages (it's not a bad inclusion for pure nature in general since it's also really helpful against drake  + ravage).  Pretty much every other deck has some kind of answer to mage spam + netherwarp; Radical listed most of them, but AoC and Phoenixes + CC work as well.

I've always been a strong proponent for rebalancing the game before release, and now that Kubik seems to be behind the idea and there is community support for it I've decided to start working on my balance proposal.
First a little bit about me and whether you can trust me with regard to game balance: 
I was very active in Battleforge from 2009 to 2011, and I played on and off from 2012 until the shutdown.  I've played on all of the (non-beta) balance patches and have watched the game's balance change and improve over the years. I've played over 3000 PvP matches in total. In 2011 I was ranked #1 for several weeks in 1v1 with my shadow/frost deck and a couple months later I held the #1 rank for a couple of weeks with my pure nature deck.  This was during a time when Obesity, DeChris, MaranV, and Freemka were active. I achieved a #1 2v2 rank with two partners (IdleAltruism and Tyderianek) using nature/frost, pure nature, and pure fire decks. I owned every card with the exception of a few PvE cards and played every deck extensively except pure frost.  My main decks were pure nature, shadow/frost, nature/frost, pure shadow, and pure fire. I've played my share of PvE, as you had to back in the days before battle tokens since that was the only way to upgrade cards.  I could consistently beat rPvE level 10. I make strategy games as a hobby and have studied and deconstructed the balance design of Battleforge (as well as with other card games and RTS) to help me balance my own games. Some thoughts on the rebalancing process:
Focus on what's being said, not on who's saying it - analyze and criticize ideas, not people.  Let's not make this a popularity contest. Being good at the game doesn't necessarily mean you really understand the game.  I've seen really good players make some really silly balance suggestions over the years.  That said, high level players tend to have a much better understanding of the game's nuances. Being bad at the game doesn't mean your input isn't be valuable.  It's possible to have a good understanding of game balance and the math behind it without having the skill or time to play at a high level (case in point, most game developers). This balance proposal will consist of two stages: 
Stage 1 involves solving major problems that currently exist in the game's balance; specifically bad matchups, overpowered cards, and bandits being weak overall.  This stage doesn't involve that many changes, but a lot of reworks are necessary in order to fix these problems which unfortunately means that these changes are more complicated to implement.
Stage 2 involves buffing and reworking weak/useless cards in order to increase the pool of useful cards and thereby increase choice and card diversity.  This involves a large list of (mostly) simple changes.
Note:
Orbs will be denoted by color:
P = Purple (shadow) R = Red (fire) G = Green (nature) B = Blue (frost) N = Neutral (any element) All changes are relative to a card's U3 stats.
Stage 1:  Solving Problems
Note to the devs: I realize that many of these changes are more involved than just changing a few numbers, but more complicated changes really are necessary to fix the few egregious problems that still remain in the game.  With the exception of Amii Monument (which I know is a longshot), I've used only mechanics and abilities that currently exist in the game.  My hope is that you can find ways to use certain cards as templates (or perhaps copy/paste data) with which to implement these changes.  Please let me know what currently is and isn't possible so that we can find alternative or compromises.
Phase Tower
The Problem:  Phase tower is simply too versatile.  It functions very well as a defensive tower, however its ability to be used for offense or to be moved to defend another location removes most of the counterplay against towers, which involves attacking another location while your opponent binds power in the towers.
The Solution:  There are perhaps some more elegant ways to rework this card, but I think a simple solution will work just fine here.  We can simply increase the card's cost in order to increase the amount of power it binds and reduce its overall cost effectiveness.  Reducing the range by 5m also eliminates a design oversight that allows it to outrange things like Mark of the Keeper.
Decrease attack range by 5m. Increase cost by 10. Treespirit (Green)
The Problem:  Treespirit is really the last remaining blatantly OP card in PvP.  It's stats are simply too high for its cost and the fact that it's an M counter creates massive problems for most T1 colors due to hurricane limiting the usage of S units.
The Solution:  By reworking the card, we can both bring down its overall power level while also re-purposing it to fill some roles that nature T1 really needs filled.  By changing the green affinity to red and giving it siege, we give nature a good counter to towers (especially phase tower) and a way to rush down instant T2 (currently many decks can rush T2 with impunity vs nature).  A reduction to the unit's HP brings its stats down to be more in line with its cost.
Change affinity to red. Change damage type from M to special. Change ability “Gifted Thorns” to “Infused Thorns”: Every 10 seconds, unit fires thorns in all directions that deal 120 damage to enemies within a 35m radius around it, up to 180 in total. Add ability “Siege”: Deals 100% more damage against structures. Reduce HP from 880 to 670. Increase (melee) damage from 400 to 500. Treespirit (Purple)
By increasing the shadow affinity's max AoE damage while decreasing its single target damage (something that would normally be a nerf since it makes it only effective vs spam) and giving it a damage bonus vs humans, we can mitigate its weakness to ice barriers and give nature a good tool to help them deal with frost mage spam.  The total damage the unit can deal is reduced, however the amount of damage that will end up hitting frost mages instead of ice barriers is significantly increased (unless the frost player spams ice barriers, in which case the nature player can just retreat and re-engage in another location).  The fact that the poison damage doesn't stack also deincentivizes spamming just treespirits.
Change damage type from M to special. Change ability “Tainted Thorns”: Every 10 seconds, unit fires thorns in all directions that deal 20 damage to enemies within a 35m radius around it, up to 120 in total (damage, including poison, hits up to 6 targets). The thorns are extremely toxic poisoning every enemy they come in touch with. The affected entity will then take 10 damage every second for 5 seconds. Add ability “Tainted Fury”: Deals 50% more damage against humans. Reduce HP from 880 to 670. Increase (melee) damage from 400 to 500. Nox Trooper
The Problem:  Nox Trooper is fine as it is, but making purple treespirit do 50% more damage to humans breaks the otherwise good shadow vs nature balance.
The Solution:  The solution is to change the Nox Trooper's type.
Change type from human to undead. Firedancer
The Problem:  The ability to shoot over cliffs and walls makes Firedancer far too difficult to deal with and gives pure fire an unfair advantage on certain maps.
The Solution:  While the ideal solution would involve checking whether the firedancer is shooting over a cliff or a wall, I'm pretty sure there's no easy way to implement this check (correct me if I'm wrong).  So alternatively, we can use a mechanic that already exists with Mortar Tower and make it so that the firedancer can only do full damage if there is a friendly unit or building near the target. 
A normal pure fire attack usually has enforcers, scythe fiends, or a rallying banner near the base that's being assaulted, so this change won't affect normal pure fire play very much.  Cheesing with cliffs and walls, on the other hand, will become much harder to pull off and can be countered by killing any units near the building that's being attacked.
This change makes firedancer about as effective as firestalker when using its regular attack.  When using it's new ability, it does a little more damage than the old firedancer.  Unit cost has been reduced slightly to compensate for the extra micro that will be needed to use it effectively and the fact that its ability can be interrupted once any nearby enemy forces have been destroyed.  Changing the damage type to S and removing the (mostly detrimental) buggy knockback gives pure fire a semi-decent alternative S counter.
Reduce cost to 60. Reduce attack damage from 100 to 70. Increase attack speed from once every 4 seconds to once every 3 seconds. Remove siege. Change damage type from special to S. Remove S knockback. Add ability “Bombard”: Activate to target an enemy structure. While attacking the targeted structure, this unit attacks three times as quickly (every second). Lasts until interrupted. Can only be used if there is a friendly unit or building near the target. (No cooldown). Magma Hurler
The Problem:  Pure fire has no good way to deal with the War Eagle + Skyelf Templar combo and also struggles against other L threats.
The Solution:  Make Magma Hurler a tier 2 pure fire unit.  This gives pure fire a reliable L counter that can also hit air units.  Magma Hurler at tier 3 doesn't fulfill its role very well since archers are generally not very useful at tier 3 (siege units and units that can quickly deal with threats are much preferred).
Change orb requirements from NNR to RR. Increase cost to 150. Remove M knockback. Bandit Sorceress (Blue)
The Problem:  Bandits have little to no defensive capabilities, which makes them helpless against most attacks.
The Solution:  Repurpose Bandit Sorceress to make her a purely defensive unit that can protect or repair power wells and monuments.
Increase cost to 80. Increase attack damage from 48 to 60. Increase HP from 520 to 660. Can now enter any friendly building, including power wells and monuments. Change “Blessed Installation”: Activate to send the unit into a friendly building. While inside the building, the unit will reduce all damage done to the building by 75%. Lasts for 30 seconds, after which the unit will exit the building with her life points restored and all buffs and debuffs removed. Costs 15. Bandit Sorceress (Red)
Change affinity to green. Increase cost to 80. Increase attack damage from 48 to 60. Increase HP from 520 to 660. Can now enter any friendly building, including power wells and monuments. Change “Infused Installation” to “Gifted Installation”: Activate to send the unit into a friendly building. While inside the building, the unit will cause the building to regenerate 40 life points every second. Lasts for 30 seconds, after which the unit will exit the building with her life points restored and all buffs and debuffs removed. Costs 15. Rioter's Retreat (Blue)
The Problem:  Same as above, bandits lack defensive options.
The Solution:  Make Rioter's Retreat a better defensive tower by giving it S and M knockback and allowing it to protect or repair buildings.
Reduce attack speed to once every 5 seconds. Add small and medium knockback. Change “Blessed Retreat”: Friendly units and buildings within a 25m radius around the tower take 20% less damage. Rioter's Retreat (Green)
Reduce attack speed to once every 5 seconds. Add small and medium knockback. Change “Gifted Retreat”: Friendly units and buildings within a 25m radius around the tower regenerate 15 life points every second. Windhunter (both affinities)
The Problem:  Windhunter's ability makes it eruption fodder.
The Solution:  Reduce self-damage.
Reduce Gifted/Tainted Sobering self damage from 300 to 250. Icefang Raptor (both affinities)
The Problem:  While frost's lack of swift units is a deliberate design choice, it can be unfair on certain maps where frost sometimes can't even reach their first power well before the opponent blocks it.
The Solution:  Give frost a semi-swift unit by making Icefang Raptor tier 1.  This should help frost to secure their first power wells and should also help them deal with mortar tower.
Change orb requirements from NB to B. Reduce damage from 820 to 650. Reduce HP from 895 to 715. Timeless One
The Problem:  Timeless One is cheap enough to be very spammable, allowing players to easily lock down any number of locations.
The Solution:  Increasing the cost of the unit and removing the ability cost forces players to both spend more power immediately for the first freeze (80, up from 65) and also forces them to bind more power into combat-weak units, making spamming Timeless Ones hurt a lot more.  This change will reward making fewer Timeless Ones and keeping them alive so that they can use their now free ability many times.
Increase cost to 80. Decrease ability cost to 0. Increase damage from 55 to 70. Stormsinger (both affinities)
The Problem:  Stormsinger's stats are simply too high for a tier 2 splashable ranged M unit.
The Solution:  Reduce Stormsinger's HP to put it more in line with other T2 ranged M units.
Reduce HP from 750 to 690. Spikeroot
The Problem:  Pure nature lacks good ways to deal with M units - especially Burrower.
The Solution:  Increase Spikeroot's damage to allow nature to kill M threats more quickly and to increase Spikeroot's usage as an M counter where Deep One is often used instead.
Increase spike damage from 100 to 110. Increase (melee) damage from 1200 to 1320. Creeping Paralysis
The Problem:  Pure nature lacks defensive capabilities and needs ways to extend their CC.
The Solution:  Decrease the cost of Creeping Paralysis so that it can be more effectively used to lock down attacking units in early T2 where pure nature struggles the most to stay alive.
Reduce cost from 60 to 50. Increase charges from 2 to 4. Deep One (both affinities)
The Problem:  Deep One's stats are too high for its cost, even for a pure unit.  This causes Deep One to often be used in place of proper counters (like Spikeroot and Ghostspears) because of its exceptionally high overall power level.
The Solution:  Reduce Deep One's HP.  Damage should be left intact because pure nature needs Deep One's damage to deal with threats quickly enough.
Reduce HP from 1650 to 1450. Enlightenment
The Problem:  Enlightenment was one of the most heavily nerfed cards in the history of the game, having its power cost increased by 90.  For PvE, the card is still very useful, and actually single-handedly makes pure decks inferior in PvE, since you can just go double nature and play any cards you want with enlightenment.  For PvP, on the other hand, the card is too expensive to be realistically used in most high level matches (even in 2v2).
The Solution:  Make enlightenment a pure nature card and reduce its cost back down to 150.  This means that you actually have to make sacrifices in PvE to use this (extremely powerful) card and this creates a good reason to play pure nature in PvE.  For PvP, the card is made viable again and pure nature T3 becomes a serious contender in 2v2.
Change orb requirements from NGG to GGG. Reduce cost to 150. Earthshaker
The Problem:  A single Earthshaker can destroy three monuments.  In combination with the above Enlightenment change, that means that pure nature can use this two card combo to destroy an entire base for 250 power, and this can be done every 30 seconds.  This can only be countered by frost spells, and the only way all losses can be prevented is through the use of either Ward of the North, or the combination of Shield Building, Glacier Shell, and Kobold trick.  Enlightenment + Earthshaker is thus almost twice as efficient as Curse Well and it has the ability to kill orbs.  This makes earthshaker unhealthy for the meta because a frost orb is always required to counter it (similar to the old wildfire, though much less egregious as a T3 two card pure combo).
The Solution:  Reduce earthshaker's damage so that it can no longer kill wells on its own and decrease the card's cost.
Reduce quake damage from 605 to 330. Reduce cost from 100 to 40. Increase charges from 2 to 5. Amii Monument
The Problem:  Amii Monument is basically cheating in PvE.  It allows players to outright skip boss fights and other parts of PvE maps that really shouldn't be skippable (at least not via OP cards).
The Solution:  Change Amii Monument so that it is a tier 1 card that no longer advances the player to the next tier, but still provides access to the selected orb's element.  For example, fire T1 could build Amii Monument to give them access to roots and hurricane, which could be combo'd with Mine and other things.  Similarly, pure shadow could build this in tier 2 to allow them to play disenchant on their harvester.  This opens up a lot of interesting possibilities and combos in both PvE and PvP, but the 100 bound power still represents a significant sacrifice that has to be made in order to build it.  A lower activation cost allows players to switch between different orbs without too much cost.  If this is not currently feasible to implement, the only other alternative I see is to make Amii Monument tier 4 and reduce its cost.
No longer functions as a regular orb, but rather provides access to the selected orb's element without advancing tier. Change orb requirements from NNN to N. Reduce cost to 100. Reduce ability cost to 50. Reduce HP to 800. Stage 2:  Buffing Weak Cards
WIP

I think that the card will still be useless after receiving a buff like this.  If we look at other T3 units with CC abilities, those abilities are always very aggressively costed when compared to spells, due to their more restrictive nature (in terms of positioning and bound power).  Examples being Fathom Lord, which has excellent stats, and a cheap paralyze (the strongest kind of CC); Swamp Drake, which has solid stats for a flying unit and what is essentially Oink for 30 power (with 2 fewer seconds to hit the affected unit without reverting CC); and Timeless One which is cheap and has a dirt cheap ability.
Twilight Hag, on the other hand, has abysmal combat stats, and even at 50 power, the ability is still worse than Oink in most cases.  A few things to consider:
You have to bind 75 power in order to use Twilight Hag's ability. The unit is occupied for the full duration of the ability, meaning that she doesn't do damage or knockback while using it. The ability only takes effect around the unit, unlike Swamp Drake and Timeless One where you have a decent bit of range to place the CC optimally.  Combined with her low HP, this makes getting her into position very difficult. If the Hag is CC'ed or teleported the ability is cancelled.  This means that the ability is completely countered by several spells that don't cost that much more (even after your proposed change) and are very likely to get more value by hitting other enemies. As a non-squad M unit, she can be completely locked down by knockback. The ability radius is actually much smaller than the aura would suggest (small enough for ranged units to hit her, charge units to charge at her, and Grigori to disintegrate her), so there is room to increase the AoE. The ability doesn't affect female enemies, as well as many beasts and some other units (mostly anything that doesn't have a male voice).  This may not be very significant right now, but as weak cards are buffed, many of those unused cards will be used and this downside will become more apparent. As far as the unit's combat abilities go, it's not even cost effective against units it should counter (e.g. Fathom Lord, Virtuoso, or even Fallen Skyelf). And the upsides:
She can't be knocked back while using her ability. Her damage buff/healing is nice, but only really does much if you have a lot of units around her (which makes her even more vulnerable to CC). Her knockback radius is pretty big, making her good for locking down M and S units. I can understand wanting to be conservative with buffs in order to not break things, but I think that if we're going to make much progress we can't be afraid to be more aggressive with our buffs.  We should be putting units into a state that puts them on par with other good units; then if they end up being too strong, we can always dial them back after testing them on the test server.  A common and effective methodology for pre-release balance (which this is) is to push the unit to what you see as the reasonable limit (some designers would argue even beyond that limit) in order to find the unit's strengths and to get a good feel for its interactions, and then dial it back if necessary.
My proposal:
I think that buffing the ability and increasing the unit's HP for more survivability is the right approach, it just needs a LOT more:
Increase HP from 785 to 1350. Decrease ability cost to 15. Increase ability radius by 5m. If CC hits more than 1 unit, it's still generally a cost effective way to counter the Hag's ability.  Pure fire has Wildfire, which easily kills her even at 1350 HP unless you cancel the ability and move her (and pure fire doesn't need any help in T3 anyway).  This is a huge HP buff, but it still doesn't put her in a normal stat per cost range for a T3 unit (Silverwinds have nearly double her current stats).
A better alternative would be to give her damage resistance and CC immunity while using her ability, along with a moderate HP boost and ability cost reduction; but that would probably be a lot harder to implement - the above solution should suffice.

I think that the card will still be useless after receiving a buff like this.  If we look at other T3 units with CC abilities, those abilities are always very aggressively costed when compared to spells, due to their more restrictive nature (in terms of positioning and bound power).  Examples being Fathom Lord, which has excellent stats, and a cheap paralyze (the strongest kind of CC); Swamp Drake, which has solid stats for a flying unit and what is essentially Oink for 30 power (with 2 fewer seconds to hit the affected unit without reverting CC); and Timeless One which is cheap and has a dirt cheap ability.
Twilight Hag, on the other hand, has abysmal combat stats, and even at 50 power, the ability is still worse than Oink in most cases.  A few things to consider:
You have to bind 75 power in order to use Twilight Hag's ability. The unit is occupied for the full duration of the ability, meaning that she doesn't do damage or knockback while using it. The ability only takes effect around the unit, unlike Swamp Drake and Timeless One where you have a decent bit of range to place the CC optimally.  Combined with her low HP, this makes getting her into position very difficult. If the Hag is CC'ed or teleported the ability is cancelled.  This means that the ability is completely countered by several spells that don't cost that much more (even after your proposed change) and are very likely to get more value by hitting other enemies. As a non-squad M unit, she can be completely locked down by knockback. The ability radius is actually much smaller than the aura would suggest (small enough for ranged units to hit her, charge units to charge at her, and Grigori to disintegrate her), so there is room to increase the AoE. The ability doesn't affect female enemies, as well as many beasts and some other units (mostly anything that doesn't have a male voice).  This may not be very significant right now, but as weak cards are buffed, many of those unused cards will be used and this downside will become more apparent. As far as the unit's combat abilities go, it's not even cost effective against units it should counter (e.g. Fathom Lord, Virtuoso, or even Fallen Skyelf). And the upsides:
She can't be knocked back while using her ability. Her damage buff/healing is nice, but only really does much if you have a lot of units around her (which makes her even more vulnerable to CC). Her knockback radius is pretty big, making her good for locking down M and S units. I can understand wanting to be conservative with buffs in order to not break things, but I think that if we're going to make much progress we can't be afraid to be more aggressive with our buffs.  We should be putting units into a state that puts them on par with other good units; then if they end up being too strong, we can always dial them back after testing them on the test server.  A common and effective methodology for pre-release balance (which this is) is to push the unit to what you see as the reasonable limit (some designers would argue even beyond that limit) in order to find the unit's strengths and to get a good feel for its interactions, and then dial it back if necessary.
My proposal:
I think that buffing the ability and increasing the unit's HP for more survivability is the right approach, it just needs a LOT more:
Increase HP from 785 to 1350. Decrease ability cost to 15. Increase ability radius by 5m. If CC hits more than 1 unit, it's still generally a cost effective way to counter the Hag's ability.  Pure fire has Wildfire, which easily kills her even at 1350 HP unless you cancel the ability and move her (and pure fire doesn't need any help in T3 anyway).  This is a huge HP buff, but it still doesn't put her in a normal stat per cost range for a T3 unit (Silverwinds have nearly double her current stats).
A better alternative would be to give her damage resistance and CC immunity while using her ability, along with a moderate HP boost and ability cost reduction; but that would probably be a lot harder to implement - the above solution should suffice.

I would love if everyone got the same quest everyday. For example: win Blight expert (100 bfp). That way it incentivise playing different map and we can find people to play these maps even with our smallish community.

I think that the card will still be useless after receiving a buff like this.  If we look at other T3 units with CC abilities, those abilities are always very aggressively costed when compared to spells, due to their more restrictive nature (in terms of positioning and bound power).  Examples being Fathom Lord, which has excellent stats, and a cheap paralyze (the strongest kind of CC); Swamp Drake, which has solid stats for a flying unit and what is essentially Oink for 30 power (with 2 fewer seconds to hit the affected unit without reverting CC); and Timeless One which is cheap and has a dirt cheap ability.
Twilight Hag, on the other hand, has abysmal combat stats, and even at 50 power, the ability is still worse than Oink in most cases.  A few things to consider:
You have to bind 75 power in order to use Twilight Hag's ability. The unit is occupied for the full duration of the ability, meaning that she doesn't do damage or knockback while using it. The ability only takes effect around the unit, unlike Swamp Drake and Timeless One where you have a decent bit of range to place the CC optimally.  Combined with her low HP, this makes getting her into position very difficult. If the Hag is CC'ed or teleported the ability is cancelled.  This means that the ability is completely countered by several spells that don't cost that much more (even after your proposed change) and are very likely to get more value by hitting other enemies. As a non-squad M unit, she can be completely locked down by knockback. The ability radius is actually much smaller than the aura would suggest (small enough for ranged units to hit her, charge units to charge at her, and Grigori to disintegrate her), so there is room to increase the AoE. The ability doesn't affect female enemies, as well as many beasts and some other units (mostly anything that doesn't have a male voice).  This may not be very significant right now, but as weak cards are buffed, many of those unused cards will be used and this downside will become more apparent. As far as the unit's combat abilities go, it's not even cost effective against units it should counter (e.g. Fathom Lord, Virtuoso, or even Fallen Skyelf). And the upsides:
She can't be knocked back while using her ability. Her damage buff/healing is nice, but only really does much if you have a lot of units around her (which makes her even more vulnerable to CC). Her knockback radius is pretty big, making her good for locking down M and S units. I can understand wanting to be conservative with buffs in order to not break things, but I think that if we're going to make much progress we can't be afraid to be more aggressive with our buffs.  We should be putting units into a state that puts them on par with other good units; then if they end up being too strong, we can always dial them back after testing them on the test server.  A common and effective methodology for pre-release balance (which this is) is to push the unit to what you see as the reasonable limit (some designers would argue even beyond that limit) in order to find the unit's strengths and to get a good feel for its interactions, and then dial it back if necessary.
My proposal:
I think that buffing the ability and increasing the unit's HP for more survivability is the right approach, it just needs a LOT more:
Increase HP from 785 to 1350. Decrease ability cost to 15. Increase ability radius by 5m. If CC hits more than 1 unit, it's still generally a cost effective way to counter the Hag's ability.  Pure fire has Wildfire, which easily kills her even at 1350 HP unless you cancel the ability and move her (and pure fire doesn't need any help in T3 anyway).  This is a huge HP buff, but it still doesn't put her in a normal stat per cost range for a T3 unit (Silverwinds have nearly double her current stats).
A better alternative would be to give her damage resistance and CC immunity while using her ability, along with a moderate HP boost and ability cost reduction; but that would probably be a lot harder to implement - the above solution should suffice.

On the topic of balancing one or several cards at a time:
It has to be remembered that a lot of cards are essential to more than one faction. I have a fear of people only looking at the main matchups (lost, pure fire, fire/nature...) and making matchups worse by not thinking about every single matchup wich is affected by a change. Imo balancing the game without a ,,3 steps forward, 2 steps back'' pace can only be done with multiple changes at a time. How else do you want to balance cards that are in top tier and lowest tier decks at the same time?

This is exactly my intention.  The whole purpose of a large balance patch is the change things up significantly.  Sure, you can win with every color, but my goal is to bring each matchup as close as possible to a 50-50 chance to win (assuming equal skill levels); balance in asymmetric PvP games is mostly about eliminating any advantage that occurs before the match has even begun and emphasizing skill, strategy, and adaptability instead.  I want to eliminate map advantages and matchup advantages as much as possible, and that can't be done without disrupting the current meta and which decks are good against which.
It will take at least months before all bugs are fixed and all planned features are restored, so we have plenty of time to test and get things sorted out.  No one can accurately predict how the meta will turn out in the end, but understanding the balance system that Battleforge uses and modeling changes mathematically (which I've done) greatly improves the chances of things being balanced from the start.  Make no mistake, though, I don't think that my balance changes (or any one else's, for that matter) are likely to be perfect right out of the box.  It always takes lots of testing and iteration to get things tuned just right, and Kubik has already said on discord that we will be testing any changes on the test server before deploying them.  I'm certainly not suggesting that my changes be implemented as-is without any testing.
I think it's actually better to rebalance several cards at once, because it allows you to see how the newly changed cards interact with one another and gives you a better idea of the game state as a whole.  Rebalancing and testing cards one at a time would take a lot longer, because while that one card might be balanced, it might later become unbalanced after you make other changes and then you'd have to go back and fix it, which in turn might break other things... it's a vicious cycle.
I believe the current approach is to collect all the agreed upon changes and put them into a big balance patch, then test and refine things until we reach a good game state.  This is how it should be done, because, as you said, making big changes can have unforeseen consequences.  I definitely think that we should go big with our changes though before the game's release.  It may be an unusual approach to balance patching, but Battleforge is in an unusual state where people have had literally years to think about balance before even getting a chance to play the game again.  We've compiled a lot of information and consensus on what needs to be changed and this is the ideal time to change all of it.

Spikeroot really is essential for pure nature to survive against this (and many other M unit threats).  Oink the mages and then deal massive damage to them with spikeroot.  Parasite (the spell) also helps since it has high single target DPS and can jump to up to 6 mages (it's not a bad inclusion for pure nature in general since it's also really helpful against drake  + ravage).  Pretty much every other deck has some kind of answer to mage spam + netherwarp; Radical listed most of them, but AoC and Phoenixes + CC work as well.

Shadow/Frost is generally considered to be the strongest PvP deck for the following reasons:
Strong, versatile, and easy to play T1. Cheap, high damage units like Nightcrawler and Darkelves, as well as very efficient offensive units like Mountaineer. Building protection, CC, and Aura of Corruption make for very strong defense. One of the strongest T3 in the game (up there with pure fire) due to things like Grigori, Tremor, Silverwinds, and Timeless One. Stonekin is also very strong due to having the best building protection, CC, and knockback units (fairly unbreakable defense with all of this).  Adamant skin + Crystal Fiend means that they can just defend until the power pools are big and then they can streamroll their opponents.
One deck that's pretty underrated, but extremely strong is pure nature.  Pure nature has some insane strength (Energy Parasite, Deep One, Shrine of Memory, and Parasite Swarm are all absurdly strong), but also some huge weaknesses: no building protection, no direct damage spells, and no high damage ranged units (except for Spikeroot, which is expensive and has to root before attacking) makes them extremely weak on defense.  If played properly, however, I would argue that pure nature actually beats every deck except fire/nature and stonekin.
Note that this is for 1v1.  In 2v2 pure fire + stonekin is the strongest combination.

Very nice guide, @RadicalX.  You've covered all of the important stuff in detail, but I do have one critique, and that is that I don't think your Frost vs Nature section is accurate at all.  I was ranked 1st with my pure nature deck back when both Freemka and MaranV were very active, so I've played literally dozens of nature T1 vs frost T1 games against them and I can tell you that it's much more nuanced than just nature getting streamrolled by Frost Mage spam.  Nature has one key card that just wrecks frost T1 when used correctly, and that card is roots.
There are actually two things that are very dangerous for Frost: namely, Swiftclaw rush and Shaman spam.  Swiftclaw rush is actually more dangerous than Scavenger rush IMO, because nature can root defending units when they run to attack a different location, which often buys the nature player enough time to kill a well.  The other thing is that Swiftclaw has very high M damage so, on small maps and with proper micro + heals, it can actually just fight Ice Guardians and win if the Frost player grabs a well.  Swiftclaw vs Ice Guardians in one location is a very close fight when the Frost player has just grabbed a well and is down 100 power and it all comes down to micro here.
This makes things more difficult than the Scavenger rush because the frost player has to commit more units to defense or their Ice Guardians will just be overwhelmed and killed.  On smaller maps where Swiftclaw rush is good (easy to run between bases) frost actually shouldn't grab a well, even if it means completely giving up map control.  What you want to do as frost is just hang back and defend while building up a Frost Mage army.  As you noted, once the frost player gets a critical mass of Frost Mages, they will be able to kite and kill the Swiftclaws with ease.  If the nature player grabs a well and tries to zone you out of the map, you just need to be patient and build up that Frost Mage army—you'll still be able to kill their well long before it pays back the 100 power investment (just watch out for defensive towers).  Frost can always defend against Swiftclaw rush, but they have to be very careful about taking wells on certain maps.
Swiftclaw rush is very powerful on some maps, but most high level frost t1 vs nature t1 games come down to Frost Mage spam vs Shaman spam.  You are correct in that Frost Mages completely destroy Shamans in a head to head fight (even with the Dryad damage reduction); but, again, the key card here is roots.  This scenario is actually very high tension and a single mistake can easily cost you the game here.  What nature wants to do is to keep the frost army away from their base, and catch the frost player when they have their Frost Mages in a bad formation—they want to root the frost army in such a way that they can pick off a couple of Mages without losing any Shamans and then heal up and repeat, dwindling down the frost forces until nature can eventually take a head-on engagement.  
First and foremost, frost wants to keep their Mages close together and in a line formation (facing the nature army) in order to prevent the nature player from getting a good root.  After that they want to try and pick off Shamans one by one with Frostbite, and they want to try and force a full-on engagement by threatening to attack the nature player's base.  Often this matchup comes down to the Frost player attacking the nature player's base, while the nature player uses their power wells/orb to absorb damage from the Frost Mages, but in this scenario frost usually wins due to Home Soil.  So nature wants to avoid this by constantly threatening with roots (keeping the frost player from marching straight into their base).  Nature can also build Primal Defender or Mark of the Keeper if they feel their base is being threatened, provided they aren't completely giving up map control by doing so.
I think that nature actually has the advantage in this situation unless the frost player has Glyph of Frost.  Glyph can save the frost player after the nature player gets a good root, and it is also a major threat to the nature player when their root is on cooldown—if nature can't run away or use buildings to absorb damage, they lose.  So what this ultimately comes down to is a war of positioning and trying to catch the other player's army out of position; one good root can end the game, and likewise, one good glyph can end the game.
Frost is generally favored when the numbers get really big (like 20+ mages) because Homesoil just keeps scaling to the point at which nature just can't do anything against it, so nature wants to be taking the initiative in this matchup, and they generally want to end it or go T2 before the numbers get too huge.  Pure frost also has the advantage going into T2, because War Eagle just decimates Shamans and Dryads; whereas Frost Mages are still at least decent against nature T2 (especially combined with War Eagles, because they can knock back Parasite Swarm).
I can't blame even a very experienced player for not knowing this matchup that well, as it is an extremely rare matchup, especially at the higher levels.  Hopefully you can incorporate some of this information into your guide; and if you want me to back up the statements I made here, I'd be glad to do some nature t1 vs frost t1 sparring once I get access to the game.

Yep, the problem is that you can't maintain that formation while moving across the map.  That's why the matchup becomes a battle of positioning, with nature always inhibiting the frost player's movement by threatening with roots.  Maybe with impeccable micro it's possible to not get caught out at all by roots, but I don't really think it's feasible in an actual match—at least when I was last active, the best frost players at the time were not able to do it.  But I guess we could argue back and forth forever over how big the frost advantage is, when it's really something that can only be determined experimentally (though actual matches).

You shouldn't grab a well in this situation.  It's just that a lot of frost players seem to think for some reason that nature can't rush them, when in reality Swiftclaw rush is quite dangerous (even Freemka has grabbed a well vs me and lost to a Swiftclaw rush, so it's not just a new player mentality).  I think it's worth stressing that you really have to watch out for this as frost.
The thing is that it's nearly impossible to have a perfect formation that doesn't allow your mages to be rooted and picked off.  Since you can't just stack all of your mages directly on top of each other, there's always going to be opportunities for roots, and that's why nature doesn't just get completely destroyed in this matchup.
Yes, but this isn't actually that hard to do and it's impossible for frost to avoid getting rooted and having at least 1 or 2 mages picked off.
Nature should always have their army in a position that allows them to intercept the frost army if it moves towards nature's base.  Since both armies move at the same speed, nature actually has the initiative advantage because root can be cast from a fair distance (due to its sizeable AoE) and takes effect instantly (as opposed to Glyph of Frost).
This is true, and one of the tougher aspects of this matchup for nature; though Spikeroot helps a lot for this.  I usually deal with this by making sure I have enough power for Oink + Spikeroot the instant my T2 is up (Oink is needed for the Lightblade).  I guess this is really tough to deal with if you don't have Spikeroot.
I still think you're exaggerating frost's advantage in this matchup.  Certainly, frost does have an advantage (especially with Glyph of Frost), but I really don't think it's that big of an advantage.  As I said before, I've played dozens of ranked games vs Freemka and MaranV with nature T1, and as I recall, I had a pretty solid positive win ratio against both of them (more so against Freemka—Burrowers/Cannon Towers are hard for pure nature); I was definitely able to hold my own, if not win, at T1.  That said, these two players are really the only good frost players I knew and regularly played against—maybe your frost T1 is a lot better than theirs.  In any case, I would also love to do some sparring when I get access to the game.

Very nice guide, @RadicalX.  You've covered all of the important stuff in detail, but I do have one critique, and that is that I don't think your Frost vs Nature section is accurate at all.  I was ranked 1st with my pure nature deck back when both Freemka and MaranV were very active, so I've played literally dozens of nature T1 vs frost T1 games against them and I can tell you that it's much more nuanced than just nature getting streamrolled by Frost Mage spam.  Nature has one key card that just wrecks frost T1 when used correctly, and that card is roots.
There are actually two things that are very dangerous for Frost: namely, Swiftclaw rush and Shaman spam.  Swiftclaw rush is actually more dangerous than Scavenger rush IMO, because nature can root defending units when they run to attack a different location, which often buys the nature player enough time to kill a well.  The other thing is that Swiftclaw has very high M damage so, on small maps and with proper micro + heals, it can actually just fight Ice Guardians and win if the Frost player grabs a well.  Swiftclaw vs Ice Guardians in one location is a very close fight when the Frost player has just grabbed a well and is down 100 power and it all comes down to micro here.
This makes things more difficult than the Scavenger rush because the frost player has to commit more units to defense or their Ice Guardians will just be overwhelmed and killed.  On smaller maps where Swiftclaw rush is good (easy to run between bases) frost actually shouldn't grab a well, even if it means completely giving up map control.  What you want to do as frost is just hang back and defend while building up a Frost Mage army.  As you noted, once the frost player gets a critical mass of Frost Mages, they will be able to kite and kill the Swiftclaws with ease.  If the nature player grabs a well and tries to zone you out of the map, you just need to be patient and build up that Frost Mage army—you'll still be able to kill their well long before it pays back the 100 power investment (just watch out for defensive towers).  Frost can always defend against Swiftclaw rush, but they have to be very careful about taking wells on certain maps.
Swiftclaw rush is very powerful on some maps, but most high level frost t1 vs nature t1 games come down to Frost Mage spam vs Shaman spam.  You are correct in that Frost Mages completely destroy Shamans in a head to head fight (even with the Dryad damage reduction); but, again, the key card here is roots.  This scenario is actually very high tension and a single mistake can easily cost you the game here.  What nature wants to do is to keep the frost army away from their base, and catch the frost player when they have their Frost Mages in a bad formation—they want to root the frost army in such a way that they can pick off a couple of Mages without losing any Shamans and then heal up and repeat, dwindling down the frost forces until nature can eventually take a head-on engagement.  
First and foremost, frost wants to keep their Mages close together and in a line formation (facing the nature army) in order to prevent the nature player from getting a good root.  After that they want to try and pick off Shamans one by one with Frostbite, and they want to try and force a full-on engagement by threatening to attack the nature player's base.  Often this matchup comes down to the Frost player attacking the nature player's base, while the nature player uses their power wells/orb to absorb damage from the Frost Mages, but in this scenario frost usually wins due to Home Soil.  So nature wants to avoid this by constantly threatening with roots (keeping the frost player from marching straight into their base).  Nature can also build Primal Defender or Mark of the Keeper if they feel their base is being threatened, provided they aren't completely giving up map control by doing so.
I think that nature actually has the advantage in this situation unless the frost player has Glyph of Frost.  Glyph can save the frost player after the nature player gets a good root, and it is also a major threat to the nature player when their root is on cooldown—if nature can't run away or use buildings to absorb damage, they lose.  So what this ultimately comes down to is a war of positioning and trying to catch the other player's army out of position; one good root can end the game, and likewise, one good glyph can end the game.
Frost is generally favored when the numbers get really big (like 20+ mages) because Homesoil just keeps scaling to the point at which nature just can't do anything against it, so nature wants to be taking the initiative in this matchup, and they generally want to end it or go T2 before the numbers get too huge.  Pure frost also has the advantage going into T2, because War Eagle just decimates Shamans and Dryads; whereas Frost Mages are still at least decent against nature T2 (especially combined with War Eagles, because they can knock back Parasite Swarm).
I can't blame even a very experienced player for not knowing this matchup that well, as it is an extremely rare matchup, especially at the higher levels.  Hopefully you can incorporate some of this information into your guide; and if you want me to back up the statements I made here, I'd be glad to do some nature t1 vs frost t1 sparring once I get access to the game.

On the other hand who wouldn't get annoyed/cynical from time to time putting so much time and work into something to give it to the people for free and then you got so many people complaining and being clever with what you could have done better...you would have to be completly non empathic or some kind of buddhist monk who doesn't know anger. I wouldn't handle it so well i think and i'm glad there are people who keep showing patience and support and are constructive if they are critical.

Surely you realize that T4 is quite bad in PvP, right?  It's not just the up-front cost that's the issue, it's the fact that you need map control and you have another orb to defend—and perhaps the bigger issue is the fact that power spent on orbs is permanently lost, meaning it is removed from your power pool.  In PvP it's almost always better to stay T3 and have +300 power in your pool than to go T4.  In 1v1, it's often better to stay T2 for a long time and some decks can actually do better without any T3 cards at all.  This is also the reason why playing a long T1 can give you a power advantage.
In any case, I completely agree that all cards should cost the same amount of gold to upgrade.  Making card upgrades more expensive by rarity or by orb cost would put pure decks and PvE decks at an upgrade disadvantage, and there's just no reason to do that.
As for having only one currency, I like the idea, but I don't really think there's much of a point.  As @Treimsaid, a single currency system would be more punishing to new, or uninformed players, which I think is a bad thing—these players will already be at a disadvantage and I think that the game should be designed in a way that guides them to make good decisions with their collections.  I do like the idea of finding the optimal card acquisition/upgrade path for your decks, but I don't think it's worth the cost of leaving new players confused and regretting their decisions.

Later on in the original game you could upgrade cards using battle tokens which were earned by playing PvP, but it was pitifully slow.  The devs have confirmed that you will earn gold (now the only thing used to upgrade cards) by playing PvP.  I did update my original post to mention that PvP and PvE rewards should be equal.
I also updated and clarified some other things in the post.