I found this comment on wowhead in case it helps:-
I had the same problem. Just found out a way: leave the group (if you are still in one) and reset the dungeon. Equip the level 200 neck and use it as soon as you enter the dungeon (so you are transformed). From there, just walk to Myza’s Oasis (you can even use the teleports). You don’t have to talk to any NPCs. The door will be opened and you can turn in the quest.
Im not sure thats it. This one video I found has him right at the start . There is also a circle at the start from the quest marker that says he should be there