Yoda never used the darkside. He is a perfect personification of what a Jedi master should be, which is a dedicated lightsider that never uses the darkside. If you think he used it when he took Dooku's lightning and shot it back, he didn't. He actually absorbed it and released it except for Dooku's final shot of lightning, which Yoda absorbed entirely. Yoda never once used the darkside of the Force. Luke and Vader(Anakin) did, however, use both sides as you said.
-Jedi Master Kir
I think you hit "new thread" button instead of "post reply".
If this is the case, let me know where you meant to post this 7& I will move it there.