The additional buff it gives is that it burns reanimated dead and their casters near you. Am not sure if I would count this one as a bug but it also burns my own reanimated dead (technically, the buff works right because it didn't say they have to be enemies). However, another bug and is really problematic is if you use a reanimation spell on a living being, the buff will burn them to death, even if the said spell actually can't reanimate the target (like the target's lvl is too high for the spell).

Edit: the buff is supposed to burn the caster too, am not sure how much is the burn supposedly but am not taking any dmg from it by using the bug but the enemies who reanimates gets dmg.