I think this is bugged. 5 PC's took the quest, only a handful of spawns appeared, no boss, no end xp, and almost no loot.
I've found the boss hiding in strange corners in some back hallways. I imagine you checked but maybe someone missed him?
Maybe, all the duergars are finally dead and all the crystals taken from the sheer amount of spam this quest endures.
Otherwise, I'm not sure what this might be.
We searched the entire place, left the QA, went back in and searched again. I have seen this before a couple times in the old EFU setting so perhaps it was a one time thing or will fix itself with reset.
We have two crystal mine quests, please be more specific in the future.
I was there. This is the purple crystal mine quest.
The prof has it right, and apparently it did take care of itself upon reset.
It happened once again just a while ago.