Holy fucking shit THAT took a lot of effort. We 4-manned all eight layers of twisting corridors over the last four days. Everything was fairly easy up to layer six. Layer seven took three attempts, wiping on the boss and floor 17. The bosses are stupidly tuned. The only reason we managed to kill layer 8's boss is that we spammed fifteen smoke bombs so none of his stuff could harm us. Along the way, I picked up the missing companions for the achievement as well. In terms of strategy, we had a druid tank, a rogue and a druid DPS along with myself. The biggest issue early on was me pulling aggro from the tank on large pulls - I was doing a sustained 300K DPS on large pulls. The other main issue were traps and just general inattention. The runs are grueling. It takes two hours per layer, so at least sixteen hours if you never wipe. If you wipe, plan for 20+. I'm honestly done with playing wow for a day or two after all this :)
A complete guide to doing every world of warcraft achievement, starting from nothing.