oh dear my eyes...

Well no one seem to mention double casting Flare which disappoints me if you consider to want top damage of all time.

Don't care much but as long as you have enough mp to cast Flare (low mp as possible) with Astral Fire III, you should cast Flare > Convert > Swiftcast > Flare. With darklight set and relic you should be able to do 2000 crit dmg with Flare. Consider it's AoE and you can do it twice with the combo above makes you a true nuker.

But that's just me playing my BLM.