I would say set your casting order like this which is how mine is =p
Banshee , SOB , Grim Strike , Ho to tactics then Vile Blade , Penetrating , Shriek Blade , Howl , Rythm blade , Lanets , Ho to rythming Curse then shriek blade. Then spam what ever is up and i cast Cob when dispatch is on. So thats my cast order

Also what aa lines you running ? Are you Mt dirge or dps Dirge in raids ?
What does your gear look like ? Your group in raid has some to do with it to. Alot is a factor into your dps so it all depends.
Now i can base 2.3k-2.4k on average now and ZW.Last night i hit my top dps with 2.8k in raids. I also do about 2.8k in groups when its setup right and ive topped 3.2k in groups.
Well need anymore help send me a message.