Hmmm.................... The greatest duelist here in terms of technical mastery is Anoon Bondara as he is somewhat (slightly) comparable to Qui Gon Jinn and an apparent master of multiple styles (not sure if all). Anoon is followed by Roan Shyrne a man who contested fiercely with a Vader who was unaccustomed to his cybernetic implants. Siolo'urmanka Is more or less equal to Roan as he actually defeated Maul (a lesser opponent) once and would have the element of surprise on his side in facing opponents with no prior knowledge of the properties of his wooden staff. Roan Shyrne/ Siolo'urmanka are followed (closely) by Tsui Choi who managed to disarm (literally) Vader despite him wielding a Cortosis blade although he was fighting Vader in a group. Jai Maruk and Serra Keto are equals as Jai performed only marginally better against Ventress than your average Jedi Master would and Serra Keto's only credible dueling feats are cutscenes that show her losing to Anakin in fairly short order.
So Anoon Bondara (technical mastery)>= Roan Shyrne = Siolo'urmanka > Tsui Choi > Jai Maruk =Serra Keto