Since I just finished leveling my affliction warlock alt, I may have a few suggestions. :)

Get the Glyph of Soul Swap and whenever multi dot quest mobs that are in the same area i.e. don't wait for a mob to die, just move on to next mob. The more you use this glyph's benefit, higher your DPS will be.

Make a macro that casts Corruption, Bane of Agony and Haunt (in this order). Open by casting Unstable Affliction and start hitting the macro button before the cast time of UA is finished. This way, you will eliminate the reaction time delay in your rotation.

Replace Drain Life and Seed of Corruption each with macros that cast Soul Burn before these spells. That way you don't need to check whether your Soul Burn is off cooldown and you will make the most use of it.

For trash mobs in dungeons, if you have 4+ mobs in a group, start tabbing to each mob and spam the macroed Seed of Corruption. You will run out of mana soon, but you have Life Tap and healers are usually skilled enough to heal you back quickly.

Haunt gives a big boost to your Dots, but even if we ignore that benefit, it still hits much harder than Shadow Bolt or Drain Life. So, make sure you cast haunt whenever its ready (which is why having it on your regularly spammed macro helps).

Please ignore the typos in that post (there is no edit button).

Your regular rotation should be
1. Unstable Affliction
2. Spam the macro (Corruption, Bane of Agony, Haunt)
3. Soul Swap if its ready and move to next target.
4. Shadow Bolt (if Shadow Trance has procced from the Nightfall talent or Glyph of Corruption - they do stack).
5. Drain Life (if Soul Burn is ready).
6. Shadow Bolt spam until one of your Dots fade or Haunt becomes available again. You will only need to do this on bosses, others die before this.

The reason why I don't recommend putting Unstable Affliction in your spam macro is because sometimes you need to use it while moving and you don't want the first spell in the macro that requires you to stop and cast.

Thank you very much! That makes me much more enthusiastic about playing my new Warlock. Appreciated.