This was raised on another blog, and I thought it was an interesting question. I don't have any answers, but these are my thoughts, in no particular order.
1. I'm a better teacher now than when I started teaching, but it's not my personal writing success that's made me so, it's my experience as a creative writing teacher plus lots and lots and lots of thinking and reading about creative writing.
2. When I started going to writing classes, I wanted someone who'd had some success with their writing. I didn't have confidence in someone who hadn't achieved publication in some form. I still feel that way, and cringe when I hear of someone teaching who hasn't actually been published (unless they've got other professional publishing experience, such as having been an editor).
3. When I was on my MA some of the feedback the other students gave was excellent, some was not. There was no correlation between the quality of the feedback and the student's previous success or experience. However, those people who gave good feedback went on to have publishing success while those who didn't, didn't.
4. There is publishing success and publishing success. Self publishing a book, however you dress it up, means you have sidestepped the quality question. I'm not saying all self published books are bad, just they haven't been through an external quality assessment process and backed by someone else's money. I've seen people announce that they are published, when actually they mean self published, or published by a vanity press.
5. I am successfully published by most people's standards, but I could no more give useful advice on poetry than I could run a marathon. If poetry was your thing, you'd do better with an unpublished but knowledgeable tutor than you would with published but ignorant me.
6. I have high standards and want my students to set themselves high standards too. Even if I'm teaching a leisure course I want them to work hard. That's not for everyone. Some people are happy for their writing to be way down their list of priorities, and that's fine - but I may not be the best person for them.
7. Similarly, I'm not a great person for touchy-feely navel gazing, although I hope I'm sensitive to people's vulnerabilities and encouraging to the tentative. Some tutors are touchy-feely and like navel gazing, and if that's what you want, why not? In other words, the personality of the tutor may be more important than their publishing history.
8. If you were writing to go through a lot of personal stuff then you'd be better working with someone who has experience of this. There are courses around of writing for therapeutic purposes, and there are people trained in this area. Their experience would count far more than their publishing history.
9. Some tutors are very sniffy about some forms of writing - I've heard of students on MA courses in particular having their work dismissed as not worthy, simply because of the genre they wanted to write in. It would be more important to have someone as a tutor who was open to what you wanted to write but was perhaps not a super successful writer themselves, than someone who was a starry literary name, but dismissed your work and undermined your confidence.
10. Related to the above, you may be sniffy about what the tutor writes, in which case you won't have confidence in what they say. You may be right, you may be wrong, but if you don't have confidence in them, they are the wrong tutor for you.
OK, so that's my thinking. What do you reckon?