Two questions...
One, I understand for sustained damage you want to put Incendiary missile up first, but isn't using TD -> IM -> RS the stronger opener? Personally, I think the most powerful part of the build is the fact that the TD and RS hit at approximately the same time when doing that. Though, I suppose it doesn't make a huge difference whether something hits in one second or the next, but that's just my preference. If there's a compelling reason to use your order, inform me
Second... you're using Rocket Punch before Flame Burst on that "opening" rotation. With the change, unless their text is wrong, Combustible Gas Cylinder needs to be on the target in order to proc PPA. The one benefit I've found to Flame Burst first is the fact that the CGC dot is applied before the check for PPA, thus you can proc PPA by simply Flame Bursting a target (even if you haven't hit them with anything before).
I've been mostly PvEing (cleared HMs on the PTS, so I had a lot of time to work with the new changes), so I haven't had a bunch of time to mess around in PvP. My "opener" is...
Thermal Override -> Thermal Det -> Incendiary -> Rail -> Flame Burst -> Rail (PPA) or Rocket Punch (no PPA)
78% of the time, I get a PPA proc by that point. If I don't, I obviously work around it to stay <40 heat, and Flame Burst when I can (unless the cooldown on RS is coming off).
Whenever I get a PPA proc, I always Rail Shot on the next global. Then, during the 2 "filler" globals, I do a mix of Rapid Shots, reapplying IM, TD, or using a 3s channel (Unload is underrated, people need to realize how important things re-applying CGC is now... Unload costs less than Flamethrower, longer ranged, and does around the same damage with at least 1 CGC proc, not to mention it applys the dot). Then, I obviously just go from there, repeating as necessary.
Another extremely useful combo with the way CGC and PPA work now... if you switch to a new target, or a teammate needs help finishing someone off and Rail Shot is on cooldown:
TD (optional) > Flame Burst > Rocket Punch (no PPA) or Rail Shot (PPA)
Huge burst, low-ish heat cost (won't screw you like a new Incendiary Missile). Plus, CGC ticks harder than IM, especially on low hp targets.