It's definitely the case, it's stated plainly in the necromant.atom file.
The problem is twofold: First that Necromancers aren't listed as being immune to mind spells, and second that Magic Shackle isn't listed as being a mind spell. It definitely wasn't in AP.
Don't forget the Witch Hunters not having the mind immunity that they are listed as having.
Thanks for clarifying, I thought I was missing something! I'll go make updates now.