Well, I have finally been playing this some, and going through on Legendary is tougher than I remember. I did the Escape form the Cartographer Map room without shooting anything. That is one crazy achievement, especially without the infinite grenades. Fortunately, I had the grunt funeral skull on along with Boom so Grunts do a lot of cascading explosions in packs. Still, it was pretty rough at times.
Quis custodiet ipsos custodes?