This is the build I used in Closed beta and it worked fairly well in both PvP and PvE. Most of the skills I took were more focused to PvP though.
I can explain each skill point but it really wouldn't make much difference for PvP specifically.
The meat an potatoes:
: is a ranged stun with a short duration, it's best used to pick off the enemy who wandered too far from their line, or to get the drop on an unsuspecting SW after you put your first few hits in and he is trying to run.
: is a Melee stun, and it seems silly as a Sentinel but you will ALWAYS have melee charging to you because you're one of the most squishy, if not the most on the field for them to attack. I use it when i see that Defender or SW moving out of the pack ready to pounce on me I target them and get ready to boot them in the face.
: This is a great skill all around. It insreaces your movement speed and allows you to find all those prowling SW's waiting for someone to stray from the pack, or to cull the weak from the pack.
: It's a quick cast buff for an increase of 1000 Evasion and VOID. I always use this when i am about to pull ahead of our line of battle into the neutral zone to pick someone off, or if I see that melee skirting around to come after me.
If you're going to spec into Detection Mastery, it's only worth the first level thus far. Level 2 only gives you an increased detection of 5 and Inner Sight gives 10 per level. I had level 3 Inner Sight and 1 point of Detection mastery in CB and saw level 29 SW's over 15 meters away.