I had problems defeating him as well, i could take out the first form but the second destroyed me.

I finally struck lucky, on the second form I summoned Yojimbo who attacked all 3 enemies on his own, stopping both pagodas, I kept paying him 10,000 gil for 3 turns and he kept the yu pagodas dead so BFA's overdrive guage wouldn't charge. He only attacked with his sword swipe, which yojimbo jumped out of the way of each time. Final time I gave him 100,000 gil and he used Zanmato, end of battle