As said, keep your regen timer on atleast 3, preferably 4, unless you have to burn. You'll do a lot more damage in the long run by adding some auto attacks into your rotation.
Most if not all the classes have been designed so you either have to stop what you are doing or use the default filler ability to not lock yourself out of your abilities.
You need to start weaving rapid shots (0 heat ability) in between your other abilities and time when you should use your heat dump. also abuse the hell out of thermal sensor override.
Using CDs near the beginning is nice. Once you have 5 stacks, I generally use whatever abilities I can, throwing in Rapid Shots every other ability. My heat will ramp up pretty high and then I just drop it all with the CD. You can do that 2 or so times a fight typically.
When you can't use that CD, I have my alacrity at a point where I can use Tracer + Rapid shots and that counts as 1gcd, so as soon as rapid shots is done I can use Tracer again. My heat won't go above 0 doing this. Use Rail Shot every 5 stacks you put on yourself (with 4pc its 0 heat cost) and unload whenever its procced. You will never see your heat ramp up. It will start climbing, but once you use Unload, it will typically drop back down.