Why can't I raise snow bears, Chaurus or drauger death overlords?I know the necromage perk in restoration would make raising the undead easier but why should I have to go to a whole different tree just to make my main skill reliable? Every single "raise dead" spell before dead thrall could raise anything so I don't know why this was handicapped. I mean as a pure necromage who doesn't use atronachs or destruction I find it very hard to survive when I can't even raise the good enemies. What make good thralls? I know bandit chiefs and vampires but what else?

http://www.uesp.net/wiki/Skyrim:Dead_Thrall#Unique_NPCs.