-Stasis is largely overlooked for use on snipers. It does not do a tonne of damage, but it will lift them out of entrench. If you spec for zero range FL in Watchman you can immediately leap and get even more focus. Use Cauterize to snare him for 50% movement for 6 seconds. It will help.
-If you are knocked back, and you have the focus built up (I usually do), hit a sniper with Crippling Throw or Blade Storm. People almost always forget about these ranged attacks. Often enough the sniper fails to knock me back until I am almost done with him. By that time, Dispatch is up and I can throw it while rooted. If not, Force Camo so he cannot target you.
-If you forget to use stasis, or it's on CD, make the sniper pay for entrenching with Master Strike. It does a lot of damage. Often enough they will simply run away from you. Keeping snipers off balance can help win a warzone. Obviously healers are primary targets, but snipers should never be overlooked.
-Don't forget to pacify snipers. For six seconds he/she is de-buffed by 90% to accuracy. That's when you can attack with impunity.
-Don't forget your cooldowns. If Rebuke is down, you may still have saberward. For 12 seconds that can help blunt his attack or avoid it altogether.
What the above poster stated is correct. Snipers and Gunslingers are usually so myopic in their pursuit of damage and the kill at a distance many don't even notice me walk up to them. By the time they DO respond it's often too late to do much. Soon you will be seeking out snipers, not dreading their presence in warzones.