Just because you've put in hours of attempts and haven't beat it, don't assume you're doing it wrong or have the wrong team. It took me pretty much the entire week it was up last time, spending multiple hours a day. Although, now that I think about it, I was able to complete it like 3 tries after Ahsoka Tano got her buff. My team was:
Lumi (Lead)
QGJ
JC
Ahsoka
Kit
The team I beat was Yoda, Plo Koon, and JKG. I focused down Yoda, then with 3 or 4 of my characters left, I don't remember, I took out Plo Koon then finally JKG.
This fight is all about RNG, so if at first you don't succeed, or at 400th you don't succeed, try try again.
On a side note, I would love to go back and try it now that I have Barriss at 7*. I'm sure that would make it much, much easier.