I'm still undefeated, my strategy so far has been to mix my strongest teams between offense and defense. If my arena team is better than theirs, I'll put it on defense in front and they'll sometimes have to put three or four battles into it, which leaves them with nothing left for my really grindy teams like zBossk, Qira/Nest, zKRU, etc. in the back. You have to compare your rosters beforehand and try to anticipate what they're going to set and what they're going to save. If you find that right balance, you can still wipe their defense and they won't be able to get through yours. Mods also make an enormous difference, make sure every viable team you have is modded, I see so many people that only worry about modding their arena team, and they end up getting destroyed because they only have one good team.
Here's my roster:
https://swgoh.gg/p/753742937/