So, as a joke/experiment, I unleashed the mechanical yeti at hakkar today (just did the quest, upcoming patch, engineerthingy I kinda want). Somehow it overaggrod the maintank instantly, and never lost aggro again. I unleashed it at 70%, and it tanked hakkar all the way to death.

http://members.home.nl/gcf.klaas/yetitank/tank3.jpg
http://members.home.nl/gcf.klaas/yetitank/tank4.jpg
http://members.home.nl/gcf.klaas/yetitank/tank5.jpg

(edit: URL fixed)