Stay at medium range with Edge. Make sure Lymle is on on healing duties. When the boss stands up on his back legs and his chest starts to glow bluish green, charge in with your specials. His chest is his weak spot.
Easy way to beat him is to just use Reimi and spam Seraphic Thunder. Also when you get her Rush gauge full use it while continuing to spam Seraphic Thunder. Doing this will allow her to never leave Rush state as it will constantly rebuild from all the hits. Remember to circle around him, while doing this so you minimize damage taken. If you need to heal switch off to Lymle or Edge to drop her a heal and if you are running low on mana just use a blackberry on her. Doing this I made quick work of him in 2-3 minutes. BTW do not get his 100% data unless you just want it for an achievment. The bonus he gives when you insert his data into a monster jewel is terrible [chance to prevent incap by fury -40 ATK + 20%HP]
A few good hits to that weakspot demolished him. Rush'd Reimi got off two Cancel'd Crimson Squall's and he just flopped over dead. xD --- "I'm detecting a strong ENERGY BURST! We can't dodge it!!"-Bacchus
I actually run up under his legs as Edge and hacked away. He couldn't hit me with any long range attachs because I was actually up under him, and he seemed to not pull off any melee attacks on me either. He was the easiest boss I've faced. --- I'm just like Jesus. I save... often!