I disagree.
Maul's overconfidence was his downfall. Even then, he still lives and comes back, battles Palpatine and puts up a decent fight. Still alive.
Jango Fett fights off the greatest duelist of all time in Obi-Wan and laters falls in a frantic arena to another powerful Jedi Mace Windu
Dooku/Grievous were dominant throughout the Clone Wars, both dying in a good saber duels against Anakin/Obi-Wan.
It is stupid to think Vader was ruined by a child. What did you think he was before Vader? Vader died redeeming himself and saving his son. Nothing about him was ruined during the PT.