Agreed with your points Mark, I believe there are still plenty of fish, based on divers reports, but they are not as aggressive with artificial lures any more. I also heard rumor that enforcement of the 'national park' rules had slipped more recently due to a management change.
It certainly is one of the more beautiful and easily accessible GT places you could visit and the latter point, as Mark indicates, is a major part of the problem.
If I had a time machine though it would be first on my list to go back ten years too, the quality and quantity in the first years was apparently scarey.