Some good advice for you thus far, but if I may add my two cents...
1. As Jenovaomega already mentioned, get the
Chaotic Skyflare Diamond as your meta gem. You'll have to have two blue gems socketed to activate it, but you can use
Purified Dreadstones to do this. It isn't so much the 21 crit rating, but the 3% increased damage on your crits helps a lot, especially as a destruction spec.
2. You have a PvP enchant on your shoulders. I am guessing this is a temporary fix until you get your inscription leveled high enough, since you are only Friendly with Sons of Hodir. Either grind rep (or buy it nowadays) with them to get
Greater Inscription of the Storm or finish leveling your inscription so you can get your bonus shoulder enchant.
3. Your staff should have
Greater Spellpower on it.
4. Again, as mentioned previously, substitute the Glyph of Life Tap for your Glyph of Immolate. Just before a fight begins, use a rank 1 Life Tap to initiate the buff without making your healers work.
5. Most importantly, if you are in a raid again and inspect a warlock that has similar or worse gear and a similar build but ends up with a higher dps, use Recount (or some variation) afterwards to analyze what they did. As Twirdman mentioned, look first to see if they got off significantly more Incinerates than you; this is an indication of too much movement, poor spell prioritization, or inefficient casting. Additionally, I noticed that you have no warlock tier gear, so you have no T9 bonuses. This may contribute to the difference in dps as well, since the other lock may be getting the benefit of the 2p or 4p set bonus.
I think if you start with this it should lead you to getting the most out of your gear and spec.