Yea it would be nice if level 5 show creature spell would say immune to charm or something. I tried out the level 5 show creature just to see if it would say anything like that but it doesn't. I have the feeling that the charm spell won't work on any leaders, sub bosses or main bosses. I want to test it out on orcs because for a non melee build if charm works on most of the orcs it would be a big help.
In other games the charm spell would be in a summoner tree. I am starting a new survivor to be a summoner with a bow as a back up. The idea is to cast skeletal wall, charm the enemies you can to fight for you, when 1 dies ressurect it to fight for you. Then when your army is larger than the enemies, you can just kick back, have a brew and let your minions do all the dirty work. Using a bow to kill the toughest ones. So in a few days I'll better know what charm works on and what it doesn't.