Cruzakei

some other good frost/nature solo rPVE cards:
- frost bite (good against bosses)
- crystal fiend, preferably green
- thunderstorm
- equilibrium
- wheels of gift (expensive and more of a luxury than really needed, especially because grinders already heal themselfs up anyway)
- giant wyrm (cheap to buy and upgrade, a flying T4 makes it easy to take out spawcamps, grinders for example often get stuck in traffic)
- revenge or stone shell or ward of the north (all three do the same job)
- ice tornado
- grimvine (a cheaper alternative than grinder charges)
- construct (only as temporary support for strong bosses like twilight infestor, you only need one for constant knockback)
Like Flrbb said, T3 is a little too big unitwise, your T2, too i think, otherwise it looks solid. You could get free slots for useful spells by replacing all the units except one T3 and maybe one T2 unit - archer and mage spam with home soil already clears a lot of bases.

Some thoughts on your nature/frost deck:
- upgrade breeding gound to level 3, asap (nature and stoneskin tend to have costly units, the bereeding ground compensates for it)
- if you want to manipulate the void in that deck, add shrine of memories (that deck has lots of spells, might worth it)
- coldsnap and curse of oink might be a bit much (both serve the same purpose). oink is faster (instant CC), but your rageflame benefits from coldsnap. personally dunno which one to keep
- your t3 only has costly units. as result it might take some time until you do have a big enough army to engage t4.
- the aggressor serves the same purpose as oink and coldsnap; aggressor does only little damage but is a great CC. personaly, I'd replace it with razorshard
- I'd add another t4 unit (you just have 2 to summon until your "long recharge penality")
- personaly, I' like healing garden very much. It's ability is global, so each spell get more efective. you just have to build two buildings to keep it up all the time...