As to Dylan as a live performer, I think that with Dylan, as with any of the mega superstar types, how much one worships/loathes the artist in question seems to color most people's perceptions of the quality of their performances.

Very few people are able to objectively evaluate musical performances of those they either love or loathe, IMO. But then, if you go into a performance without the extreme emotions one way or the other, but just with anticipation for someone you heard good things about, or enjoy their recordings, I think it is much easier to give objective reports on the performance.