Looks like some people here have a massive L2P issue. Fighting a sentinel? He will likely pop rebuke, so dont use dots. CC him for 6 seconds then wail on his *** for 20% more damage. He popped saber ward? Pop your own defensive CD, his saber ward CD is 3 minutes... He stealthed? It's only 4 seconds, leave dots on him too. He popped Guarded by the Force? Well at this point there goes half his remaining HP, just pop a medpack and finish him off.
I leveled a Commando first to 50 then a Sentinel to 50 (all before 1.1). If you are ranged and having issues with a melee, here's a tip: Play a melee, learn how they function. That's how it worked in WoW, especially high-end arenas. That's how it works here. But somehow I get the feeling nobody in this thread who played WoW got over 1500 anyway so it's a moot point. Learn to play.