The heavy affliction spec just gimps your +crit. SoC grinding is about direct damage bursting which is +sp dam and +crit. I like demo better for grinding since you get soul link and other pet boosts. Destruction is probably viable for SoC grinding, but I've had good luck with demo. Just do some standard 7/43/11 build or other varient.

Or, again, you can go the siphon life route. Its pretty well documented as a solid way to clear SM too. Again, just a lot more micro (have to dot each mob twice verus planting 3 SoC's on a group of 20'ish).