I have got my warlock up to level, with a average item level of 334; however I cannot seem to grasp playing a lock since cata. My dps is super low in dungeons, to the point of embarrassment. I have switched talent tree on and off, currently Im destro/demonology. I have put add ons such such Dottimers and others. (I couldn't figure out the ForteX - whatevere it's called).

I can't seem to get a good rotation and am literally banging my head up against wall. I make sure my 3 buffs are on, I put up dots so what the heck am I doing wrong? I also make sure to SF every 15 sec - I even have a addon that beeps everytime I should shoot it again.

For destro I had succubus glyphed w/ lash of pain. Now I have Imp glyped; however, I don't he is helping my dps much. I had wanted affliction/destro but have been told affliction is usually for PvP.

If you go to the elitist Jerks website, they have forums on each class that gives rotations, etc and will tell you everything you need to learn about your class.
Here is the one for warlocks:
http://elitistjerks.com/f80/