w00t! I just beat him yesterday with the following strategy:

Butz:
Knight/Dbl Grip

Lenna:
Hunter/Blue

Cara:
Samurai/White L. 6

Faris:
Chemist/Summon L.5

Basically I just used Butz for attacking, Lenna for casting spells like White Wind and Aero3 and attacking on occasion, Cara for curing/casting shell/gil toss and Faris for keeping the team alive with Phenix and attacking with Bahamut. Plus I kept her HP high by having her drink Giant Potion so she didn't die once. I had some difficulty here and there but Neo X-Death was no match for my team.