Unfortunately Freeze is only useful for its binding ability; the potency of Fire II is stronger on even one mob, so to use Freeze instead of getting back into Astral asap is a loss.
This is further complicated at 70 when Flares and Thunder IV become even stronger than Fire II, so as long as Transpose is off cooldown, it is best to forego your entire Astral MP pool using Flare (or reapplying Thunder IV if it's about to fall off and the stuff has a while to live).
