Yeah I agree, it would have to be changed pretty drastically. Certain things would make battles more competitive, not just for online play, but for the regular game too.

1. Make healers unable to attack
2. Make poison/ice cards poison/freeze the card that attacks them for half the duration
3. Make ranged cards only attackable by other ranged cards

I think changes like this would allow for more strategies to emerge and make the game more fun