i just beat the mess out of it.its easy when you use gambits.
1.allyhp=<50%-cure\cura
2.ally-any-raise\pheonix down
3.ally-any-esuna(if you have it,or you can use single status ail.gambits)
4.foe status=hp critical-atack
5.foe-any-atack

these gambits are good for fighting him.prioritise healing and killing weak enemies