I just did this dungeon and I want to state that I loved it. But the mobs after the spiders are level 16 and the bosses range from 17-20. This is NOT a level 11-21 dungeon. I would say 15 and 16 is pushing it.
It should be in the same level category as Wailing Caverns and Deadmines. I couldn’t give feedback in game, so I am giving it here.