if you haven't figured out yet, i use light, fang, hope. Light to blitz one side then fang naturally blitz the other side, hope to heal/synergize. I've heard some people using light hope and vanille for the easier stagger with commando/ravager/ravager, but ionno. I just use the eidolon when I get all my chars in red zone. took me 2 tries. when he uses destrudo btw, just time your attack that when he starts to attack, you are attacking him so he like flinches a little, stops the attack, or heal right when he starts hitting.