The roachs of arena:Mother talzian and Enfys nest/pest

Hi OP

You actually already have the "Counter" to Talzin/NS teams, you just need to shuffle some things around!!

First of all, zeta Palpatine, he will be one of your best arena zetas in the game for god knows how long.

Take out ventress and zombie

Use zPalpatine (L), Vader, Thrawn

Other 2 - I'm not sure what you have but best in slot would be Darth Nihilus and Sion, if you don't have those maybe use Tarkin, TFP or Raid Han, to be honest those 3 could probably beat NS by themselves.