Black Mage Dps Rotation Guide! in 90 Seconds!

[Umero]

nobody speak about the MP tick clock, which is asynchronous, mastering the tick can greatly improve your dmg

thus TH3 is too long to cast, and you re delaying your fire phase, resulting in dps loss

Agreed.
Sync your casting rotation with the GCD along with mp tick to yeild the greatest Damage Optimization.
It's very hard to explain. But that's the key point.