If it's using the same MP cost as Flare, do also remember that Mega Ethers (which I personally have in abundance from level 50 dungeons) restore 800 MP, perfect for one more cast. But, I haven't gotten into all of that to really play with.
Back here at 70, prior to these Umbral Souls and Aspect Mastery, I'm still sorta wondering at where Freeze might also fit in besides the aoe rotation. During down time, phase changes, or just moving through dungeons, while you're still Transposing to keep Eno going, I keep trying to think of what's the best way to get rolling again while you're sitting on 1 stack of AF/UI. Previously, I might start as if I didn't have it anyway. B3-B4-F3 (Thunder as appropriate) [doesn't apply to large aoe situations]. But, it should/would be faster to go Freeze-B4-F3, right? You lose the B3 potency, but it's the quicker way to get full stacks of ice.
Idk. Something about that particular quirk of the skill makes me think it might end up fitting in somewhere unintended/expected. Could be wrong. I'm not a great theory crafter. But, from the old idea of "as much as necessary, as little as possible" with regards to time spent in UI, the thought just keeps nagging at me that Freeze could be part of the "quick reset" for our rotation, getting back to square one.
Which, also somewhat makes me wish we had a Fire spell that worked similarly to fill fire stacks quicker, when your rotation/stacks are out of alignment. But I suppose maybe that's where a F3 proc comes in.
