It's probably slower here so the SM gain would take longer time, to keep the SM income slower as this patch is to stay.
"In retail", as everybody loves to mention, there was limited time before SM would become obsolete thanks to upcoming Cataclysm expansion. In retail, ICC wasn't farmed to this extent (this long, and with the same efficiency) with 30% buff.
In Warmane, there's no expansion coming, the ICC is farmed with great consistency. So more and more are getting SM, but nobody is replacing it ever.
If SFS drop rate would be same as retail, there would be even more ret/pala/DK's running around with SM's.