I never got to stagger him, and I just finished the fight for the 2nd time. I used Lightning, Fang, and Vanille and kept the Com/Sen/Med or Com/Sen/Rav para up while he was attacking, and when he guards I switched to Com/Sab/Sab to get his buffs off then hopefully slap slow and deprotect on him. It's really slow going, but I still beat the recommended time by 3 min. If you're really well developed on the crystarium though you could use Rav/Com/Rav with this character setup and speed up the kill a bit. And just a little friendly advice: Syns are overrated if you were using one.