I have greatly enjoyed reading the three Making of the original trilogy books by J. W. Rinzler. I just finished the Making of Return of the Jedi. The books are written from the point of view of the time the movies were made, not from a historical perspective, and so it cuts away a lot of the revisionism that has taken place over the years.
On July 17, 1981, Lucas, Marquand, Kasdan, and Howard Karaznjian sat down for a five day story conference on Jedi and a transcript was made of the story conference.
I never really liked Yoda fighting in Episodes II and III. I liked him more as a Force mystic, a wise guru, like Gandhi. Apparently, Lucas used to agree with me:
Lucas: Also another misconception is that Yoda teaches Jedi, but he is like a guru; he doesnít go out and fight anybody.
Kasdan: A Jedi Master is a Jedi isnít he?
Lucas: Well, he is a teacher, not a real Jedi. Understand that?
Kasdan: I understand what youíre saying, but I canít believe it; I am in shock.
Lucas: Itís true, absolutely true, not that it makes any difference to the story.
Kasdan: You mean he wouldnít be any good in a fight?
Lucas: Not with Darth Vader he wouldnít.
Kasdan: I accept it, but I donít like it.