Your spec isn't bad, but I've found that for PvP, Scorch>Fireball in almost all ways. As such, I'm partial to a scorch/fireblast focused build, such as
this one. Here are the things I really like about it:
-Scorch being fast cast, takes full advantage of Impact.
-Scorch has a higher crit rate than fireball when properly talented, meaning more use out of Ignite.
-With Imp Scorch, the enemy gets hurt more and more the more you hit him. meaning that at the end of the fight, that's where the real damage is. Same goes with molten fury. A properly timed fire blast will hit for a lot of damage if you hit him with one when he's at 20% or less with a 5 stack of scorch.
When you have a surpise opportunity, Pyro will fit the bill nicely.