AoE from 50 through 67:
Thunder II/IV, Fire III, Fire II, Fire II, (Fire II again if enough MP to do this and still Flare), Flare, Transpose repeat.
Don't Blizzard III in this situation; it's an extra single target action and you want to get back to AoE fire spells ASAP (all the splodies). Even under Umbral Ice I, the time spent casting Thunder II/IV and Fire III should get you enough MP to Fire II, Fire II, Flare again.
If you have Convert or appropriately potent ethers available, you can Flare, Convert/ether, Flare for an extra splody fire phase. For an obscene level of splodiness, Triplecast Flare Convert Flare ether Flare.
