first off you are in PvP gear on armory, that being said you are pretty much saying your main issue as destruction SMF uptime. You need to cast it so it has time to travel to the target, hit, and rebuff you. Remember Soul Fire's damage pr cast isn't 0, so even if you clip soul fire buff, its still better then letting it fall off. Rather too early then too late. Cast it at a safe time, before Fading Lights and such. Doing an extra incinerate over loosing soul fire buff is a DPS loss.
If you put the main things as destruction on one hand, its Conflagerate on CD, roll good Immolates (redo during heroism + haste trinket proc) and dont loose Soul Fire buff.
Morchok remember to multidot with immolate / corruption if you can reach it from the middle, else it's hard to do any proper DPS here. Only Morchok + Ultraxion can you give you some indication of DPS, rest of the bosses are weird and bad for warlocks and raid dps testing in general. Ultraxion is also about the kill and RNG and who logs the kill can change your DPS.
Spine i wouldn't want to comment on Destruction since i dont find it viable if you want to push DPS on tendons, it simple isnt good for it.
Madness is impossible to do good DPS on now, because of the nerfs making multi dotting horrible and add whoring impossible.
I dont think you should bother too much with Dragon Soul, it's a shit tier and we will have 5.0.1 at some point where all warlock specs and spells get revamped to complete new standards, which means we can barely use any of our base knowledge now. It becomes easier to play and there isn't as many tricky situations to maximize DPS as there is now for a warlock.
Overall you said it, try to optimize not loosing Soul Fire buff, and be sure not to waste Conflagerate time and get big Immolate's rolling with haste trinket / heroism.
Keeping track of Soul Fire buff, i use TellMeWhen to give me a big icon showing exactly how long is left, so i can precast in time depending on the boss.
Good luck trying to improve!