I’ve come across a small hole in Dornogal after jumping down from the flight master towards the trading post, with some rocks and brush. It’s well obscured by brush and easy to miss. For smaller classes (gnome), this resulted in the inability to leave the hole. This hole is above the building the Transmogrifier is in that is next to the trading post in Dornogal. Coordinates are 44.91, 53.66 on the Dornogal map. I’d love to leave an image in here showing it, but I cannot submit links.
Here it is - location described by OP
r/wow Floor missing in Dornogal above Transmog Building Below Flightmaster