The bug in this quest happened after one of the updates. It wasn't here before. May be they screwed something up when modifying the monsters and such in and around this area in one of the updates. Hopefully this problem gets sorted out as I hate running back and forth in this quest.
Happened to me, too. If someone in the party doesnt have the quest it wont work.
Not true.
Done this quest twice now with two different Characters. First time was with henchies, no glitch beat it first time.
Second time was two days ago, 2 other guildies and the rest henchies. One guildie already had the quest done and we did it fine on second try. First time through was our fault not the glitch. Mhenlo got to the spot before us cause of a wrong turn and got killed.
I have to add that my first three runs at the mission were with a guildie who had completed the quest... so perhaps there is something to the having a person that have not done it in the group.
I did not have this issue prior to the patch yesterday though...
I did this quest last night around 11p ET
Had no problems at all. Went in, killed hte 4 or 5 groups, went back to the Temple and was in and out quick.
Was the first time for me to do it too.