I've been going with the Necro/Lock build for PvP since I hit 50, but last night I decided to try out a pure Lock build (51 Lock/15 AM). I have to say, it's a hell of a lot more effective than the hybrid build with Necro, mainly b/c I can actually kill more ppl rather than just burn them down for a teammate to finish off.

Yeah, you lose the SP when not going further into Necro, but ED and Defile more than make up for it, especially now that neither one has any CD's. Also, when going all the way into Lock, Neddra's Influence gives a bigger boost to DPS. Survivability is aided by putting pts into Vitality. I think I'm going to stick with this build.