The card "Parting gift" is labelled wrong.
It says "while in play every unit killed deals 1 damage to it's enemy." But the effect is reverse: the owner of the killed creature suffers 1 damage. Well, it was not funny to find that out while having about 80 peasants on they're way to the enemy ... fix it please :-)
Also this game works against clichés :
I picked the necromancer starter first because i thought it would be the "spamming" deck, but in fact it is the one with the least "spam" value - whereas the "holy paladin" was disappointingly weak and cheap. The demons just sucked.
The pacifist style of playing is really unrewarding. Most upgrades allow you to kill humans much more efficiently, but only few do help you with that non-violent way of playing. Maybe you should implement another skill tree, one for the violent and one for the pacifist way of playing.