The Anakin/Dooku duels are non-sense if you consider the movies. That's for that they created Ventress (and also Durge), to provide a opponent to Anakin that is dangerous but that Anakin can fight and defeat to gain experience. The fight in RotS make no sense if Anakin and Dooku clashed every week during the CW.
Yes I agree with this completely. The phrase, "My powers have doubled since we last met Count." always bothered me because of how often they clash in both the CW and the brief exchange in Labyrinth of Evil which takes place right before Episode III, which means Anakin doubled his power in less than a week. It works if the last time they fought was Geonosis or even once early in the CW, but he faces Dooku twice on Naboo, once on a ship, and once on Zygaria all AFTER he was knighted so presumably halfway through the CW at least. Dooku also shouldn't have been close to the front lines nearly as much, he was busy keeping the CIS together, fomenting dissent and recruiting Dark Jedi to serve as his proxies. Like you pointed out that was the entire point of Ventress, Durge and Grievous(and to a lesser extent Sora Bulq and his cadre of Dark Jedi), they fought FOR Dooku so he didn't have to. In this way they still kept Dooku as a high standard far above these antagonists while still giving the heroes foes to improve against to eventually REACH Dooku's level by Ep III.
However with CW we get Dooku routinely getting in fights and having trouble with fighters that should be FAR below his skill and power set. The Nightsisters that attack him minus Ventress have never fought with sabers before and they are facing the best duelist of his generation, Ventress and Savage are both much weaker and inexperienced than Dooku. Anakin -while having lots of raw power was countered early on by Dooku's experience and finesse, but we don't see this in CW.