I see so many healer struggle with the Vault, and back in 3.0 knew many who had trouble

Then I tried it on WHM and...had no issues. Trash, as long as the tank didn't overpull (which can happen in any dungeon), was easy to heal, and the last boss wasn't bad either (the big problem most had with the dungeon)

Running it a few times I did figure out what the main issue is with the dungeon; the other players. Especially the DPS. Found if they couldn't dodge, or kept just taking a lot of damage (cleaves, the vuln on the portals, etc) it became *much* harder to heal. And as I ran more Vaults leveling, I saw it again and again. Parties with people who could dodge and take minimal damage had an easy time. Parties with derpy DPS or a bad tank...had a much harder time.