Ok. Let's see. I'll suggest two classes. Because two classes fit, but one way better. Before I say anything, how do you feel on a Sent and Sin? After you answer, you'll have these suggestions. Leave that Warrior blank tho(without AC).
Well, here it goes.
On Sent(lvl 37)(combat) : First thing I noticed - i suck at PVP with it. At PVE i finished the first chapter of story line without problems, but around lvl 30 i started to make more research regarding the rotation, because on a long run in a fight the surv is pretty low. Now after the first mission of chapter two (some expert moobs) i died at one of them due to 3 sec delay in the rotation which really showed me that maybe i should re-spec to another tree, but the combat one is the one i like most....
On Sin (lvl26) (deception) : All the aspects until now are so fine that i can't believe what i saw on sith forums that deception is not good for lvling. I don't have any problems neither in PVE or PVP , mostly due to the fact that i use my companion as a tank. I notice that if I tend to go before my companion i loose very fast health points, but still i have time for the ultra defensive skills and i can avoid death with half of my HP all the times. As for PVP i was able to get kills even when i joined at lvl 10, i still wonder if later in the game i will reach to a block as it happened with the Sent, that's the reason i started the other 3 chars, but i really would like to know on which of this 5 to concentrate mostly in order to have a better game experience.