With 1500 units I think you can do it. Your problem is that you don't have very many viable (5/6*) champs. I agree with Djin. Rank Ibom, definitely doable might have to take the quests slow. Idk been a while since cav.
If I were to do a variant, which one would you recommend?
5, 6, and 7 are the easiest. They have different requirements so just look at the requirments and look at your roster. Looking at your roster I think you could take the villain or hero variant.
Comments
And I think you can do it.
Guardian has high energy resistance. So he should be able to manage the 6.1.2 Ultron boss.
6.1.6 Sentinel fight is just very long. There's nothing particularly hard in that fight.
You also need a bleed immune champ for the biohazard sentinel in 6.1.2
And 4* and below champs can't be used in Act6.