How to beat ZSavage?

Don't leave him for last. Use his debuff stealing thing to your advantage. Dot up and thermal detonator up someone else after debuffing him. Avoid hitting him if he's not in stealth so he can't cleanse himself (only cleanses himself when you crit him). Between the debuffs you put on him, and the ones he stole from others, that should be enough for Boba's execute to take him down.