About skeletons: this is a suggestion.
About liches: they have this in the original, it makes sense to give them a zombie infection ability, just for consistency, but you removed their plague.
About archers: this is from the original. Apparently, they were supposed to have a double shot, I would give them Storm (although that would be 4 chance-based abilities).
About angels: they fly fast enough.
I understand everything about Inferno.
Another question: what makes the Archdemon ability so good?