Aesthetically definitely the Vault, Arboretoreum and Sohr Kai, these places are just gorgeous. I mean that might be my most hated class, art history, that I suffered through, speaking, but the Vault is very very pretty to watch. Arboretoreum, while mechanically Blegh was honestly one of the most gorgeous dungeons I've ever seen, and I absolutely love the design of Sohr Kai, but that might just be me digging ruins in general, even moreso when they float. Music-wise a special mention goes to Fractal Continuum tbh, when I got the Orchestrion scroll of that after a very fun run I nearly squealed in delight there.

Mechanically speaking, Sohm Al was really fun, even if it's just SCoB mechs watered down. I loved the first and final bosses in Pharos HM; Xelphatol and Gubal HM have got to be my fave Ex Roul dungeons up to date too. Special mention here goes to Lost City HM, that one spiced it up mechanically a little, those bosses are still fun.

A can of worms I'd gladly never run again is Neverreap (3 weeks and two days... in a row... 23 days in Bird Hell, and this is coming from someone who went to Bird School, which is for Birds). Seriously that one wins by a landslide. Next up is Aethero, that place is a DRAG and I really really don't like Forgettable Larry and Iggy Azalea, that boss fight's just stupid (too bad one run = one Singing Cluster... so I'll get it even MORE on 60 roul now, joy of joys).

If I had to pick an overall favourite, though, it'd have to be the Aery. No, it's NOT because Estinien's in there. That entire dungeon is just music-wise, aesthetically and mechanics-wise the single best one in Heavensward, but that's just my opinion (okay Estinien's a factor too)