I agree that no death magic for good seems right thematically. Unless you feel the ends justify the means, in which case I question your goodness level!
I've been thinking, what if the Evil players had Traitors, that is secretly Neutral players within their midst? The Traitors would have to betray the Evil players at some point. However I guess you would need to include some kind of condition to make sure that they don't wait until Good is dead before acting. Tell me if this is simply too complicated though.
This would essentially make it a find the assassin game for them and you could tweak the number of traitors for balance. Not exactly sure if this will work, but I'm just fishing around for balancing ideas.