Why doesn't Savage Opress have Night-sister synergies as well as Sith?

I too have the same question in mind but then.
Savage was trained by the night-sisters to avenge Asajj. But he sort of steps over her. He became apprentice to Darth Maul and followed his footsteps. That is why he only sith.
While Ashoka in a way sided with Asajj once she left Jedi temple, sided with Asajj who was also thrown away and deserted. Ashoka had been a Jedi, so the FORCE was blessed with leader synergy of both. :wink: