This ^^ is insanely situational and is such a minimal dps gain that it is not even worth struggling to master. I mean the only time where using this would be a great benefit is if you are wiping to bosses at like 50k health.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
When should I cast Unleash Elements, and what does it affect?
Unleash Flame, the Flametongue-based attack from Unleash Elements, does a nominal amount of damage and boosts the next Fire spell you cast by 30%. UE's single-target damage is pretty low right now, so it's generally not worth it to cast under most circumstances.
There is a "trick" with UE that allows both LvB and FS to gain from a single cast of the spell, which makes it just slightly better than a LB cast, but this applies in only one circumstance: when LvB is off cooldown just before the FS DoT is about to expire. Using this trick under any other circumstance is not a DPS gain.
-http://elitistjerks.com/f79/t110309-elemental_cataclysm_discussion_patch_4_3_a/

