Have you seen the video, Kamikaze? John Myung is fairly enigmatic in it. But he's no good on camera. You get the feeling he's hating every second of it. Although he's a great teacher and explains things well, I thought he tends to go over the same things a little unnecessarilly.
For example, when he's teaching an exercise that Petrucci had shown him for working on trills, he takes you through each permutation of it for each finger, when he could just show you one finger, say something like "now do that with each finger", and then move on to cover something else.
He should have watched Petrucci's Rock Discipline video for a lesson in good video-making.
I've seen a lot of so called instructional videos, and a lot of them either only show you how to play the artist's specific solo's from various releases, or else they're just a platform to show off a little.
Granted you can glean information from watching them play their stuff. But Petrucci's video shows you so much that's to do with the fundamental mechanics of playing rather than just copying his chops. I've had that video for ages and I STILL find it has a lot of offer.