There's nothing to suggest that Krayt possesses the absurd reserves of Force amplified power of the Chosen One, which is the only real evidence to support the oft repeated claim that "strength can wear down Dooku". Remember that Tyranus can casually defeat Grievous, and there's never any indication that his arms are ever sore afterwards.
No, Krayt may be skilled with a saber, but Dooku's prowess in that regards is repeatedly cited as being prodigious among the prodigious. There's only so much Krayt could have improved in his technical mastery from the A'Sharad that was never considered by his peers to have such a talent, and I don't recall his ever taking on the opponents that Dooku did. I don't recall Krayt ever handling the likes of Obi Wan and Anakin at the same time, and tooling the former in a Force grip while breaking the latter's guard and kicking him away simultaneously.