By the beginning of ROTS anakin is a tier 9 duelist and by the end of the movie he’s a solid to high tier 9 duelist and force user. Kenobi was an 8 as of ROTS. Ventress even in this incarnation can be scaled to high tier 7 to low tier 8. She’s not beating Kenobi let alone anakin. Any incarnation of ROTS anakin (normal, zone and knightfall) would fodderize ventress.