by GeekJock
They are all balanced IMO. Nothing needs to be done further.The ones which are only allowed to be done X amount of time per turn is their balancing mechanism. (ex Cyborg has two things which can help him so he can only do each once-- any more any it would not be balanced).
Most are situational and the key is to balancing your own strategy around trying to maximize your use of them vs going away from that in your deck when needed.
None of them are OP and none of them stink.
I would say don't over think the game it's a thirty min card game. If one person gets lucky with a Hero the game is over quick, shuffle up and play again.
I have won and lost big with all of the champs and have not seen one which is OP. I HAVE seen ones which I like to use more but that's a different story entirely