The double flare rotation by which I mean

~ Transpose -> Flare -> Flare -> Transpose -> Flare -> Flare -> Repeat forever.

Is the highest AOE damage in the game. It requires good timing but by no means precise and is incredibly easy to maintain!

Here's a video example of the wonderful Junpei Gunso demonstrating it
https://www.youtube.com/watch?v=9fiOG5axoVo

Pay attention to his MP and the timing of the casts and you'll see its actually very easy.

This Rotation, even with the casting delays when waiting to line up timing is significantly higher than casting fire 2 ever and of course even considering a rotation where a single target cast of fire 3 is used would be laughable, as even a flare without astral is still hitting multiple mobs (fire 3 600 damage vs 1 target = 600 damage, flare 400 damge vs 3 targets is 1200 damage example).

Any time you have 3 or mobs alive, you gotta do this