Honestly, other than MP and HP, stats don't really matter in FFIX. You could have 20 STR vs 32 STR on a character and cause rather similar damage on same-stat weapons. So, Ozma is really stat-independent. And it REALLY is RNG more than anything else in that fight. You could just go into the fight with 0 abilities equipped and melee him to death, or you could go in with a perfectly optimal setup and get creamed in 2 rounds. (2 because Auto-Life)