After defeating the boss, the script didn't fire at the sealed door. Wasn't getting any lag or anything so don't think it's an issue of that sort.
I would have to say its just you RwG, Worked the other day for me. Just need to kill the boss
Probably doesn't work the second time it's taken in a reset or something.
I played a paladin a couple months ago who experienced the same bug. I remember reporting it at the time, but it was on an alt account and I can't find the post. The 2nd time in a reset thing sounds reasonable, as I know another paladin had done the quest before me that reset.