Ok, you can check my gear prior (seeing this you made me go and check mine to make sure i didnt take something off, everything looks fine btw). If you're just going for the clear, for the first few rounds you want to just use chakra, the little damage dealt will be healed. Once the dark debuff wears off, you can autofight until the end (click ifrit so you fight him first). If you want the long sword mastery, you need to bring someone else into the fight who can hide, check this list out
http://exvius.gamepedia.com/Hide see who you have and use hide and attack with ling, then hit repeat over and over until its done. the first few rounds are the only ones that could potentially hurt/kill, afterwards its invincocity. If you're going for the moogle you'll have to do it on a separate run, bring 2 units that can hide, one with each esper needed (ifrit/siren), and when the bar is full sacrifice one of them ;P