Here is a team with which i just finished CLS event - successfuly.
I used STH as a leader, made a bit of a mess to my arena mods, but after couple tries it workd out
I think this is the bare minimum if you want to do it, i had to do a lot of adjustments to mods, and be a bit lucky on the successful try, so that my STH would survive with 90% hp to the 3/3 phase, so that he could pump up TM to my other heroes.
Had to repeat the ObiWan tier few times, but it wasnt really an issue, but i think that G9 for ObiWan is the bare minimum, i survived just so so, with less then 10% hp left, after couple of failed tries - it was just matter for trying it few times untill Vader scored a little less dmg
The hardest part was was the last phase of last tier - 3/3.
If you have any questions, feel free to ask i ll be glad to help
Hope it helps you guys, in case you too dont want to invest extra gear and purple ability material into heroes you will probably never use
Good luck you all