http://web.archive.org/web/200211291...ww.graffe.com/
The Uber Mob Resistant chart puts him at a 4/6 on Magic resistance. Which is a "Lures are never resisted, normal magic spells resisted often".
But that is not an "immune to magic spells" tier of resistance.
With Malo / Tash / Occlusion / Bard Tash Orb (WTB bardstacking) - You should be able to stick slows occasionally. It should just take a few shots at trying even fully debuffed.
Setting him magic immune is bad mmkay. Let Necros actually lifetap and stuff. Plus not classic.