We ran it on Nightmare and our DM said ours was the first zero deaths run that he had seen.
We had a Paladin, Druid, and Cleric (me) all chipping in for the heals. We succeeded all fights, and only pushed on one puzzle.
And STILL, it was utterly brutal. We walked into the last fight with all that push damage, and then lost initiative and immediately started eating huge amounts of incoming damage.
I've got a "Buff/Heal, never Swing" style build of UR+ and I am still positive that if it weren't for my lenses letting me split heals, there were people who would have been dying. We were just barely hanging in there at the end, and we had exhausted just about everything.
A fun, tense, challenging dungeon to say the least. If I had any doubts about the Cleric Legendary Neck, this run had me immediately ordering my Eldritch Bar so that I would have the last of the components I needed. Definitely my most challenging one to date.
For the record as well, we ran it with no Rogue, so we had no access to the Rogue clues for the puzzles. And nobody had done the dungeon before, so we were all flying blind. Those were particularly some rough solves, especially the final one. I still have zero idea what we were supposed to be doing, but after the first failure, we realized we just couldn't afford to keep guessing, so we healed up and then prepared for the push.