Obi Wan also used Ataru when he beat Maul. He didn't become a Soresu expert until he was defeated by Dooku in EP II, but I still don't think he got a chance against Dooku's Makashi.
The fight against Maul is actually the reason Obi-Wan adopted and mastered the Soresu Form. He was able to see in retrospect all of the failings of Ataru and decided to utilize Soresu instead.
Don't get me wrong, Ataru is great if you have ample room to maneuver. It is why Yoda was one of the fiercest lightsaber duelists of the Order, his small size allowed him to capitalize on even the smallest of open spaces, turning a confined space into his biggest advantage against his larger opponents.