Pulled Fei (Dark KFG) should I replace Sigmarus with her for DB10?

I just recently pulled Fei and I was planning to build her for Dragons B10 and Raids along with PVP using Violent Revenge which I currently have on my Sig.

Fei might not have as much raw damage output, but her ability to ignore defense on her 3rd that can potentially put out massive damage along with counterattack and ability to remove buffs with her second, Make her seem rather phenomenal at DB10.

Sig does good damage, but he is fragile and very slow and I don't ever use him in PVP or HoH/ToA due to these problems.