Raid orbs do refill on levelups.
For my first go at the ELT version I'm going to bring Cecil, Ling, Refia, Gilgamesh, Noctis, and if I can find one, a friend Yun. I'll tweak the team after seeing if I need more tankiness from stronger fire resist, or can drop some of the support and go heavier dps. Everyone on my team will have at least 50% natural fire resist before buffs from equipment, espers, or natural stats.
Yun was really made for this encounter it seems. Natural fire resist, paralyze immunity, beast killer, and the ability to equip the tamer's whip (more beast killer). A whale Yun with his own TM, Champion Belt x2, Kaiser Knuckles, and a Tamer Whip is going to tear up Ifrit so hard.