I've had the good fortune of having multiple lessons each from Scott Lee, Gene Albrecht, Stevie Moore and Stan Shuffett. Obviously, the playing levels of each is a bit different. Despite what some would try to say here, Scott Lee can play at a very high level. Perhaps he could have even competed at the pro level had he chosen that path earlier in his career. Obviously, the other 3 guys all are very high level players.
I've learned a ton from each of those gentlemen. All 4 are worth every dollar they charge and then some IMHO. Gene's deal is Perfect Aim so that is his focus. Interestingly enough, each of the other 3 think the stroke is most important and are superb at teaching it. Each also agree pretty much on the basic fundamentals of the stroke.
Bottom line, I think each of those gentlemen could potentially help just about any level of player. Dependent upon the person, their capabilities, fundamentals and weaknesses, one might be a little better than others. However, again, I think each would bring something to the party.
I hope , at some point, I can take a lesson from Jerry Brieseth, Mark Wilson and Ray Martin. I didn't get my Engineering degree and achieve Professional success from one teacher and/or Mentor. Literally hundreds and thousands of different people have contributed along the way. Arguably, I've enjoyed more professional success than 95% plus of those I've learned from but that doesn't mean I'd hesitate a second to listen to advice from any one of them today. As far as pool goes, I've learned a ton here at AZ reading threads, watching people's home videos and buying books/DVD's people have recommended. Dr. Dave isn't a Pro but his VEPS DVD's should be in any serious pool enthusiasts library IMHO.
Honestly, I don't think the issue should generally be about the Instructor but rather more about the Student. Too many people are close minded, lack commitment, are lazy and have an ego that won't allow them to learn. They're looking for the mythical silver bullet. The greatest teacher in the world can't make chicken salad out of chicken shit.