I just relied on Rinoa Zell and Squall. I used no Holy Wars- just entered the fight with low health and slapped some Invincible Moon in there. Then just let Squall and Zell go to town. Zell, by the way, can do more damage with his limit break that the Renzokuken, if correctly implemented. Second time through when I defeated Omega, it was barely a challenge at all. But I love FFVIII ^_^
Unfortunately it causes me physical pain to refine down my wonderful cards, so I can never bring myself to do it.