The best solution to ur problem is Venom. When it comes to act5 Venom is MVP, if u have a 4* rank him up and go finish the job. He can carry u not only to 5.1 but to elders bane title.
That's honestly one of the easiest chapters to beat in Act 5. The only advice I can give you is to use a high damge dealer and end fights fast. Someone like Rouge or anyone else that has lifesteal is pretty useful as well