I have tried various specs on my locks.

When I got some gear the spec I found vastly superiour was 7/43/11

Reason for this:

4x felguards is VERY helpful in bg. Fire and forget on random clothie and he's basically dead (actually miss this after I started playing shamans instead)
Shadowburn - Must have for a boxer as a finnisher. With 4x of them, you should be able to make a kill each time you use it right.
Improved lifetap - When you are running with a priest, this is very helpful for downtime.