(all damage to flame taken at the start, when it couldn't deal damage in the same turn)
Honestly, if this game added some motivations to play the other cards; some unlocks, and maybe more enemy modifiers to add difficulty, I could see it becoming quite popular even as a paid game.
And (sorry for all the comments) super important, I think many would agree:
Some heroes' attacks take forever to resolve. No joke, you attack once and wait 1 whole minute or more just for it stop. That's a bit much, I think. Flame made me feel it a lot as I soloed him.