I have had three professional ASL teachers. One was Deaf and the other two hearing. I'm sorry to say the Deaf teacher was not very good. She was wonderful when it came to Deaf culture -- my first exposure to it -- but her method of teaching was extremely outdated. Basically it consisted of giving us lists of vocabulary. My notes from that class are just pages of words I wrote down. No explanation of grammar, nothing. I didn't remember anything from that class afterwards.
My hearing teachers were excellent. They have been in the field for more than 20 years, have a deep understanding of Deaf culture, and are very well respected in the Deaf community.
I am not generalizing, this was just my own experience. I have sat in on classes with Deaf teachers (not as a student) who were excellent. My point is that just because a teacher is Deaf doesn't automatically mean they will be a better teacher than a hearing person. There are good and bad Deaf teachers and good and bad hearing teachers.
I have, of course, had wonderful Deaf teachers, but they were not professional teachers. They were the members of the Deaf community who would sit and chat with me at Deaf events or one-on-one tutoring, and were so patient and encouraging as they put up with me butchering their language as I learned. So you don't even have to have a great teacher to have a "great teacher."