Don't know why the forum didn't show me this thread when I clicked new.
As it happens I've already spoken to you about this in-game, the staple of FBTTW spec relies on you keeping LB up constantly and never wasting a hot streak. Easier said than done with the amount that's happening in-game.
I use the hideous Burnout mod to track my Hot streak countdown, the timer on living bomb and it also has a scorch meter for ages gone by. Sometimes that still isn't enough so I've had Miks Scrolling battletext do a very distinctive noise whenever I gain the Hot streak proc.
Something that might be worth looking into which would affect your dps is
when you're casting the pyro from Hot Streak?
* Do you wait for the counter until it's about to expire and fire it at the last second?
* Do you shoot a fireball and then shoot the pyro?
* Do you ignite munch?
The best way to maximise the hot streak damage is to fire it as soon as you can, thanks to the noise I can:
1. Cast a fireball
2. As the fireball leaves my hand, I use the pre-cast indicator in Xperl to manipulate the lag and allow me to start casting my next spell without having to wait for a GCD.
3. The fireball I cast in number 1 hits the target, it procs hot streak which I am made aware of by the distinctive noise / combat text.
4. As that 2nd fireball is about to leave my hands, I pre-cast the Pyro so that the fireball and pyroblast "leave my hand ontop of each other, and continue casting fireball.
It reads more complicated than it is, but what it boils down to is using the correct timing and pre-casting, you can sneak the pyro into your rotation without having to wait for any sort of GCD, and continue casting FB uninterrupted.
If it reads a little tricky I'd be more than happy to Training Dummy if for you on vent