Force: Full potential Savage can ragdoll either one of them but I'd reckon 2 powerful sith might be too much
Sabers: Feral's weapons are pretty useless against both opponents; the best he can do is stand back and try to distract them. Savage crushes Dooku and takes out Vader if he works quickly
All-Out: Feral insta-dies; Savage probably severely injures both Sith if not he takes down one. I can see him killing both in their standard mindset if he's at full potential.