"Legacy Dungeon"? It's just an area, mate.

Get the underground areas out of here, they're not even remotely dungeons. They have the flask refills on wiping out enemy groups, which is a key aspect of the dungeon structure, especially the full-on legacy dungeons.

Subterranean Shunning-Grounds is basically a full fledged legacy dungeon, specially if you count the area past Mohg. It's much larger than the areas listed alongside it and loops on itself a lot.