A balance in the gameplay. I believe that some cards lack counterplay. Like sure, some thing s MAY counter a card that is proposed to be op, but not enough cards can actually do it that it, so it has a slight advantage in more matches than not. Because of this, many players tend to use these cards over other cards/strategies. Balance may also involve the pvp vs pve scene, where some cards are very strong in pve, but almost worthless in pvp, or vice versa. I want more variety in the gameplay of battleforge, and without the need of actually adding more cards, there are plenty of cards there to use, but not enough of them are deemed viable for various reasons.
That is what I think.