Gamma Fl4k vs Dr Benedict

Need help on this fight if anyone is around? His immunity to Radiation damage nerfs my entire build and makes this fight literally impossible.

M10, PC

What kind of Gamma Fl4k? Can you post your build. I ask because with level 65 Fl4k, I believe every build would now involve TPI and Megavore. If so, you may be able to switch action skills easily and on the fly. Use Fade Away.