BLM

[Allyrion]

i think more than most here are assuming hardcasting a higher rank spell will do more overall damage
this is incorrect

I cast Thunder III cause it looks better.
I'm also fairly certain things like trying to hold out a thundercloud proc to reduce dot clipping or maximizing your firestarter procs by interrupting your fire 1 casts (or especially blizzard III when going into regen) makes a much bigger dps difference than this.

The tooltip on the thundercloud buff implies square probably meant for thundercloud to be determined by what was hard casting. If it's not that in-game, they'll probably fix it.
Thunder 2 hardcast + Thunder 3 thundercloud proc might add something interesting if the proc wasn't so damned low. I think this whole debate is a bit overstated, even for serious min-maxers.