http://www.torhead.com/skill-calc#301bMZMsZfhMbdGGMs.2
Single target rotation:
Incendiary Missile
Rail Shot
Rocket Punch
Thermal Detonator
Flame Burst
Rapid Shots
The key to the Pyrotech spec Powertech priority system is to remember the following:
Maximize Heat regen by staying below 30 Heat as much as possible.
Use Rapid Shots if above 30 Heat and Vent Heat is on cooldown.
Keep the DoT from Incendiary Missile up at all times.
Use Rail Shot on every cooldown.
Use Thermal Detonator after Prototype Particle Accelerator procs.
Follow the priority list and use higher priority abilities as often as possible.
Obviously PvP is going to be dynamic enough to where you cannot at all times stick to it, but it's a good foundation.