I always figured that you would lose DPS when double flaring on two mobs. Well, not two but triple flare maybe. I take it you use ethers?
AF3 - Swiftcast Flare - Convert - Flare - Mega ether - Flare?
I always feel uncomfortable when I have to use transpose, seems like such a waste of time. But I can see it working.
I don't know what would be more beneficial. To double flare, use your mega either or whatever and start casting blizzard III or going triple flare and transpose.