
Why did Sidious consider his lightsaber skills so superior that he considered the weapon a toy, even though there were better swordsmen than him?
I don't know about him, but in his shoes, with that viewpoint, losing in this type of duel would be truly humiliating.
Meanwhile, I have the impression that although Dooku's ability to hold his own against Yoda worried Sidious, he didn't learn much from it, which is partly why he later got his ass kicked by Windu.
Sure, only the absolute elite could have threatened him (as even three Jedi on the council fell in combat with him within 10 seconds), but I still feel like the guy overestimated himself. While this is perfectly natural for dark side users, Sidious didn't exactly make me feel like he underestimated his opponents.
Couldn't he have simply sparred regularly with Dooku to advance his swordsmanship?