Decent start. However, IMO (and I'm commenting both on the OP spec and some of the other suggested ones) :
You only need 1 pt in Shadow Embrace, its only really useful effect is to make drain life more effective.
You don't need the 2 points spent in Imp Health Stone, they're nice, but not really worth 2 talent points unless you have nowhere else to put the points when your making a demo spec. The point in shadowburn is only really for PvP and/or solo questing. Amplify curse is pretty, but not really useful in most situations. (I find the only real use for it is a curse of doom on curator =P).
Next: only 1 lock in a given raid really needs malediction. So, talk to the other locks in your guild (or the raid leaders) and find out if you really need those 3 points in there. If one or two other locks already have it, you can spend them elsewhere.
As to where to spend those points you just freed up from Amp curse, malediction, Imp HS, shadowburn, and Shadow Embrace? I would highly recommend Suppression. Granted, it doesn't help your SB spam when your not refreshing dots, but it greatly reduces the need for extra hit, and getting dot resists (and fear resists) is lame. Id rather see a SB resist than a Death Coil, Fear or even a corruption.
Here is a very solid raiding spec for someone with T4 equivalent gear. I have seen this get around 1000dps on Mag multiple times with several different raid class compositions.
http://www.wowhead.com/?talent=IEMrVMfkVtboZxx0xM