I think you may have hit upon why it's so bad.
There's nothing wrong with the dungeon at all, it's actually kind of amusing, until the end fight. The conceit is ridiculous, even relative to a typical D&D adventure.
I'm 100% sick of the lazy deux ex machina "solve the puzzle to kill the boss" **** that's infected so much of the content.
A hint to Turbine: there's no class in PnP called a "Solver".