Omega Weapon was relatively difficult for me...probably cuz I didn't use a Hero (? dunno what those are) or Holy War...or The End (I've never seen that with 7 or 8 play throughs...not once). I had around level 70 - 90 characters, lot's of status/element junctions, and high spr/hp ratings...All I remember is that Medigo Flame was annoying as hell.

:\ Aura, Meltdown, and status buffs saved my life.