Might help you to know what you can drop and still do a rotation.
The skeleton rotation:
GCD01 Incendiary Missile (reapplying the elemental DoT)
GCD02 Mag Shot (venting 5 heat and making next Power Shot instant)
GCD03 Power Shot (making next Mag Shot free)
GCD04 Mag Shot (venting 5 heat)
GCD05 ------ Filler Slot
GCD06 ------ Filler Slot
GCD07 ------ Filler Slot
GCD08 Unload (making next Mag Shot free)
GCD09 Unload continued
GCD10 ------ Filler Slot
Serrated interrupted? Let it go. Maybe do it later. Not essential for the rotation. You want it for damage but if you can't do it then you can't do it.
Unload interrupted? Doesn't matter, you got the Mag Shot reset on the first tick. The second Mag Shot reset is with an instant Power Shot so you can't be stopped. Do not forget that you NEED to fill the GCD of an interrupted Unload with rapid shots or something or the next reset will fail because there wasn't enough time spent.
Incendiary can be moved to any empty spot and TD can be put in anywhere.
Burst is from both dots, triggering Supercharge (for its extra burn and autocrit on MS) your TD and a PS/MS/PS.
Apart from that you just try to do your basic rotation and if a target dies continue exactly where you were on the next. There is no way to "reset" on a new target without waiting out cooldowns (or spending more heat that requires you to cover with a resource cooldown).