And that's why I asked if you had a PREVIOUS save file to go back to. Like, the Via Purifico or before.

If you don't, your best bet is using Tidus and Yuna for Haste/Hastega and having Auron as the main attacker, Tidus as secondary attacker/healer, and Yuna solely for healer. O'aka is on the bridge, so you shouldn't run out of Phoenix Downs.