This is my rotation which ive never had a problem with:
CreepingTerror>Affliction>DF>Reckless>ForceLightni ng(x2)>CD(with Wrath)>FL rinse repeat
Also a bit more in depth, if I'm not wrong Crushing Darkness is the hardest hitting dot? So you want it to take the most Deathmark charges.
Having creeping terror and affliction eating away at deathmark charges while you channel 2 force lightnings instead of 1 means Crushing Darkness could miss out on a few Deathmark charges. However that's not hugely important, just perfect priority talk