This duo will have sh1t sync energy. I see this playing out similarly to Dooku vs Kenobi and Anakin on Oba Diah initially, only this time Dooku won't be able to run away when he begins to tire.
Dooku would have to resort to telekinesis or martial arts to get Kenobi off his back in order to deal with Maul due to the former's impenetrable Soresu as this point.
Separating the duo shouldn't be too difficult considering how uncoordinated they'd be with Maul's aggressive juyo, coupled with a cumbersome saber staff, trying to mesh with Kenobi's defensive Soresu all while trying to land a blow on a master of footwork and strike-dodging.
Kenobi would be forced to go on the offensive to keep up and aid Maul, which would in turn expose him to a variety of tricks up Dooku's sleeve. Remember, it's whenever Kenobi gets aggressive that he gets manhandled.
I see Kenobi as a hindrance to Maul more than anything. Hell, Maul and Savage made a mediocore team to begin with. Just rewatch Sidious vs the duo. They were uncoordinated in their attack sequences and easily separated. Same can be said for their Florum fight with Kenobi.
Dooku has a better chance of winning when they're together IMO.
When he downs Kenobi, it'll just be Maul v. Dooku which is the determining factor.