My suggestion, keep the important abilities next to your toon at the center of the screen, I play a marauder annihilation and i keep 3 abilities near the center of my screen to remind myself to use them once they are off cooldown. It'll take sometimes getting use to but believe me, it's rewarding and the most fun out of any class i've pvp with.
If you play annihilation like I do, you only need to keep track of rupture, annihilate, battering assault and overload saber, when all these 4 are on cooldown you can just spam slash or use ravage/choke.
For defensive measure, always pop cloak of pain when you start taking damge, you should not have any problem with this, treat it like the trooper reactive shield, use force camo if you are getting focus, this will reset the enemies target on you and they normally just switch target . Undying rage for the OH **** moment or for crossing fire in huttball.