LUTHERS WALKTHROUGH:
well i beat him lvl 62 without and revive items, granted it took me some 50 billion tries so im used to the guy. i use fayt, cliff, and roger. all of them have laser weapons with orchalim stacked on them to the infinity power. (i chose laser weapons because they can be used by any charater, great for leveling those weak ones). anywho for me the key was shielding set on standard. i suggest putting everyone on opposite sides of the field on manual and tackel him one person at a time. and only use reviving items if you are about to die with only one person left, otherwise the AI will get itself killed.
his attacks: when he uses a heavy technique just scootback he will sideswipe the area in front of him. if he is taking longer than that run around him in a circle, he will shoot a lance in your direction (if your moving it shouldn't hit you)
his symbology:
laser beams, when he says it find out who he is going for and move them, easy enough. if the target is fayt you can use demention door, timing is crutial here.(this is a good time to hit him once and hard if it is another caracter)
skills:
expansion force and flaming divine(he will say "behold true force" for expansion force and "wallow in dispair" for flaming diving) are his favorite but are on the light setting so just use your shield and stun him, then hit him with (i have fayt, cliff, and roger) Fayt: demention door, Cliff: arial assult or acrobat locus, Roger: flying torpedo (flying torpedo is the best here because when he initiates his next attack it will be cancled by him falling down.
perfect syemetry ("data should behave as such") : just move away, far far away, really far far away, you get my point. and when he is getting low on HP he will use
Insanity prelude ("i'll show you my most powerful program"): this one hits hard and 8/10 times only the person your controlling will survive, mabey. when he says it move away from the sides but not dead center, a ball will come into the center then spike-like pillars jet up from the side. at this point in time get between two of them, as close to the edge as you can and pray.
and that's it, hope it helps, have fun :D