Some mobs are quirky. Like Vampyrs only seemed to wanna use Bloodrake above a certain HP%. Plus for something like **** a part of me felt the mob was less likely to use it if it didn't have a debuff on it to cure. These, of course, may be exceptions, but mobs have been shown to have some reactionary behavior to their AIs... like shadows popping Dimensional Death after you WS them as long as they have TP.
Violence good. **** bad. Yay America.