I am lost. Why would a Storm dispel work on a Fire Spell? You need a dispel that works on Fire. I purchased some Treasure Card Fire Dispels in the WC Library for Briskbreeze Tower.
The Efreet puts a very special Weakness on its target - that lowers the target's next damage by 90%. If you want to avoid the weakness, you have to put a Quench onto the Pyromancer before they cast their Efreet.
A Dissipate will do nothing, seeing as the spell is Fire, not Storm.