Zarchery, my best advice since you have a MNK, is actually to MNK burn it. I know you tried already, but basically we went in 4 x MNK (most of us wearing the pink gear that supposedly is a no-no) with a DNC and a SMN with Alexander. PD + all 4 MNKs 2 houred right at the beginning and spammed multi-hit weapon skills. It literally was dead in 40 seconds, no deaths. The longest part was buffing up with Ifrit, Garuda and Alexander.

That being said, I really hope they tone this BCNM down, it's just a limit break quest.