An easy way to beat ifrit if you have a RS mage weapon.
Use Rinoa BSSB
Have Edea with MM (the darkness spell that ups Magic).
Maximize Edea MP and survive ability.
Have 4 other characters who has no other job than to keep Edea alive and lower Ifrits resist. So if you have SG and a bunch of good Medicas then you can probably win this easily.
Edea basically needs to do 13 actions.
1. MM
2. Rinoa BSSB
3. The ice burst action (should do like 7K-8K * 4)
4. The ice burst action
5. The ice burst action
6. The ice burst action
7. The ice burst action
8. Rinoa BSSB
9. The ice burst action
10. The ice burst action
11. The ice burst action
12. The ice burst action
13. The ice burst action
I basically went
Tyro (SG) - Curaja, Break Dance
Vanille (Protectaga Medica) - Curaga, SHELL
Relm (SSB) - Curaga, Protect
Quistis (SSB) - Magic Break, Mind Break
Edea (none) - MM, Blizzaja