Thank you both for your input.
Ok, so what I gathered: A Jedi Team will cost me ranks in defense, but could do good in offense. Though it takes ressources.
For now I am farming JKA, QGJ, Aayla. I will hopefully get Yoda in the next event. So the team would look something like this (as soon as I get Anakin and Aayla to some stars): QGJ, JKA, Ahsoka, Aayla, Yoda. Maybe substitute one for B2 or RG. I will only farm B2 after I get Aayla to 6 stars though. But B2 seems pretty solid, didn't have him on my radar.
Right now (in GW and occassionaly in Raids) I am running IGD as Lead as I already have him at 6 stars g8. He does as much damage in AAT as Ashoka, to my surprise. Just a shame, that his counter is only 35% and that useless 35 Defense...
One more question: Is it possible to change the arena team outside of actual battles? Did I just miss this option?
And one more thing: Zeta is only farmable with Tarkins Ship? Not Mace and/or Ackbars?