From the sounds of it, you are a week or two older then I am, and possibly on the shard created before mine.
I run a pure ( most of the time ) Jedi team for Arena, and not gonna lie to you mate, it is not easy at all. Having no taunt, really puts you at a disadvantage a lot so people can pick you apart. A Barriss lead, although will keep things up on the health, will not do a lot on the offense. I do recommend hanging on to her, but using her after you get her Zeta if at all.
I run counter, with IGD on lead. I do not have GK yet, so will not be using him until I am rather older in the game. ( level 76 currently 34k ish power rating and stay in the top five pretty normally )
Healers are phased out more and more, so the Jedi healers are on their way out by our level. So no Lumi,. Ahsoka hits like a truck, so good there ( with one minor heal )
The rest of the team I use QGJ, Aalya ( awesome Jedi ) and soon to be JKA while using Old Ben or Boba Fett ( to handle Baze/Chir ) in the mean time while I get that farmed out for JKA.
Yoda is great for offense, find his AI bad for defense, where most of the problem you will run into your Jedi team will come about ( at least IMHO )
If you are more interested in hearing more, shoot me a PM