Game is pretty much perfect.
Only thing I would bother to change is, I think that every time you defeat a wave you should automatically get first turn against the next wave.
It doesn't make sense why if an enemy dies from burn/poison then the next wave gets to attack before you do; while if they die from one of your random casts you get to move before they do. Also it's annoying to kill the wave down to 1 guy then let him live so you can kill him on your next turn, just so two of you guys get to attack before the enemy wave.
Other than this, it's really perfect.