i agree the fight is easy however i think the way i fight is not that 'correct'. i am running around spamming my skill when its start its beam attack. so it took a rather long time per fight. and usually only oliver survive since the rest always die after reviving them so i don't really care them after that
The fastest way is pretty much to stay close to him (and behind him) with Catastroceros, using the physical attack power up (War Cry or whatever it's called) and then using the rock moves and some physical attacks. When he uses the beam you can switch to Oliver (who should have two light attack-boosting scales) and toss Astra at him. He can be beaten in under 5 minutes like that.