I'm having best results with the following:
Living Bomb on three things, scorch the tank's target, Blastwave, Flamestrike, Dragon's Breath, Cone of Cold, followed by fireballing and Hot Streak Pyros till dead.
On Bosses, it's mainly keeping Living Bomb up, Scorch, Fireball and Hot Streak Pyros.
For things that need to be hit hard (typically bosses), I go with Mirror Image+Trinket+Berserking (assuming you have a Troll), Living Bomb, Scorch, Frostfire Bolt (With the glyph for the DoT), Normal Pyro, and Combustion, followed by Fireballs.
I don't know how great it is, but following this strategy I'm doing something right as I always lead the raid in damage.
____________________________"Do you know what "nemesis" means? A righteous infliction of retribution manifested by an appropriate agent. Personified in this case by an 'orrible c*** :