I couldn't find a thread till now for this, but is the Healer-set better for Shadows to pvp?
The 4-set bonus is much more usefull I think.
After casting Power Word: Shield you can't be slowed for 4 seconds is much better than 5% faster cast on Mindspike/blast, because now I can get away from the DKs, Warriors etc while they stand in my comps. frostnova.
Also the stats aren't that bad. There's haste on it and you can reforge the spirit to haste too. So you'll be on 5% hitcap with a lot of haste.
I'm playing with a frostmage (just some fun till MoP starts, nothing serious)