Caster mobs not regaining mana?
 

I seem to be experiencing this: When a caster mob has been up for at good amount of time, it "runs out" of mana and will not be able to cast on you. If you aggro a caster mob right after it spawns, it will have mana enough to cast on you. I think that caster mob mana regen might be off.

I've experienced this in many places, most notably in Droga where almost every mob is supposed to be a caster. Camping the Warder by clearing the dining room, and not once did any of the casters cast on me on the first round of ph clearing.

Is it possible that they are using all their mana on self-buffs over a long period of time and never meditate, merely stand, so that their standing mana regen is not enough to compensate for the mana spent on self-buffs?

I was thinking the exact same thing. Seems plausible!