BLM's Blizzard 4 needs a potency buff

[Rongway]

I'm a "false beginner" BLM ; I'm confused in the second rotation as to what spells to use during ice phase to be sure you had the 2 mana ticks then ? When Xeno isn't active I mean, and if you casted thunder III again at that time wouldn't it be clipping the DOT quite largely ?

You have 1s after Blizzard III, 2.5s casting Thunder, and 1.5s casting Fire III, so short of 5s total when accounting for spell speed. You need t>3.0s and t≤6.0s to get a second tick, so there's an okay probability that you'll get the two ticks. However, in the event that you only get the one tick, it's still just barely a potency gain over the intended rotation if you do an ultrashort rotation for that one time only.