Buffs are a must-have in this. I totally recommend having a paradigm with Hope's Synergist and Lightning's Medic. Start the battle out with that, get all your buffs applied while Lightning keeps the team alive. Make sure you throw a Libra in, too. After that, switch between Slash and Burn (Com-Rav) and War and Peace (Com-Med). Slash and Burn will build up the combo meter fastest, but you'll probably take a lot of damage and need Hope to heal you. Keep up those two as long as your buffs stay up - if they drop, switch back to Med-Syn (I think it's Symbiosis, but I forget). I think I had to stagger it twice before I killed it. A fairly difficult battle, but if you make sure you get those buffs out and actively switch between paradigms to both keep the chain gauge building and keep your HP up, it's doable.