A teacher should be also someone who is a guide, a role model that not only teaches musical facts but also addresses personality values - here it feels to me like Marsalis himself may have some deficits in respect to his "being teacher" attitude.
Incidentally, I saw Brandford a few years ago and during his master class he was talking about the fact he still gets lessons. His story went that he was a on a gig and a saxophonist walks up to him at the end and says it was a great set but he was surprised Brandford could get a note out of the instrument with his technique. After talking to the guy he discovers he is a classical saxophonist and Brandford ended up starting lessons with him which he said he was still getting the time.