Mastered the three ultimate FFX fights, with cid mission. First one wasn't very impressive.
Geosgaeno fight for the Cid Mission I used Paine, Braska, Lulu, Wakka, Yuna. Paine used Celes BSB as a RW, then just spammed the burst commands for ~20k damage per round. Braska and Lulu used chain fire/ice for 20k damage per round. Wakka did his debuffs then died like a bitch. Yuna healed a few times then joined Wakka in the afterlife. Overall the CM was very easy thanks to his multiple weaknesses. After seeing the fight, I should have brought a group hastega RM, which would have given Yuna the speed to keep up with healing, and would have prevented the deaths. Still, I'd rank this as one of the easier CM's.
Omega Weapon I thought was also one of the easier U++ battles (if you have access to stacking magic breaks). His damage is entirely magic or gravity. Instant death resist accessories heavily mitigates his gravity attacks, and I was able to stack up -170% magic breaks (-85% after boss resist) which was over the cap anyway. Having his magic broken all the way to the cap lowered his nukes to 300-700 damage each, which wasn't very threatening. That said, I noticed he had extreme speed, and even though his nukes were nerfed to small amounts, it still added up just due to sheer frequency. I can see this U++ being a nightmare for anyone who doesn't have access to multiple magic break SB's.
Setup I used for U++:
Cloud -- Waterga Strike, Lifesiphon -- Motorcycle BSB (pure damage)
Vaan -- Mug Bloodlust, Thiefs Revenge -- Ark Blast BSB (-40% mag/def)
Agrias -- Lifesiphon, Shellga -- Cleansing Strike SB (-50% atk/mag)
Ramza -- Power Breakdown, Fullbreak -- Shout (+50% atk, hastega)
Relm -- Curaja, Protectga -- Lakshimi SSB (medica + regen) -- Lionheart materia helps a ton on the healer due to constant aoe
Roaming: Wall