I'm a Sentinel that doesn't use the force powers. (So far, no Rebuke). I use vibroblades. I figured melee is rough in pvp as I don't have an invis skill yet nor I do have a knock down (or stun that works....). I want to give pvp a try, but it's not exactly easy to run melee dps w/ only 1 immobilizing cure that doesn't work against repeated snaring.
I might check it out at level 30. I did far better in SW battlefront in vehicular combat.
If it is your first time PvPing in this game, Sentinel is probably one of the worst classes to play, especially in lowbie PvP brackets. It takes a while to master the class, and it is also one of the ones that doesn't come to fruition until a little later, specifically because of defensive cooldowns and survivability.
That having been said, if you learn to play the class whilst you're levelling, you will tear people apart if you start to play in PvP around level 40 as a Sentinel, especially if you run Combat skill tree. The burst in that spec is amazing
Focus spec can also be effective at lower levels, since it has good AoE damage. But it is being nerfed in the 2.7 patch, so it's better to learn Combat, in my opinion.