After trying for just shy of two weeks, I finally beat Palom's EX event with full high scores. Probably the hardest battle I've fought so far in this game. What finally cleared it for me was a maxed XIII team of Lightning, Vanille, and Sazh, with Ifrit summon and a 5-turn Vaan friend. Saved all abilities until the final wave, summoned Ifrit half-way through the damage phase on the first lizard, used everything Lightning had to kill him, then summoned Vaan for the second lizard. With an attack boost from Sazh, Vaan absolutely destroyed it. Feels good.
Also beat Marie's EX yesterday on my first shot. Tidus, Eiko, and Sazh all MLB. Tidus' debuffs were huge for damage and Eiko is necessary for HP damage repair. Used Ifrit again and forgot which friend I went with because I didn't use them. Found it the easiest EX so far but that's mostly due to lucking out with the perfect team for it straight away.