When Tavion was Desann's apprentice, she would be beaten by Komari Vosa easily. As Desann's successor, if she didn't have the Specter of Ragnos, Vosa would win, barely.
Tavion just isn't that powerful.
DF
Darth FaunusBoss
How would Tavion lose power?
SE7
Se7inProtegé
Komari was nearly defeated by Jango Fett, after which Dooku Force Pimped her. Tavion on the other hand was pretty decent. Just because she was Desann's apprentice makes her no weaker.