Chiming in on MDC as an Islander's fan. I'm not a big fan of him, only because I don't like prospects whose skating needs work. MDC has the shot, the hands, the IQ, and the work ethic, he just has to work on his skating and he knows it.
This was a pretty good article
https://www.nhl.com/news/michael-dal-colle-preparing-for-biggest-offseason/c-281130882
Anyway, in my opinion he's still a solid prospect but when asked why Isles are higher on Barzal it's simple. Guy is a great skater and when you have great skaters in camp they get noticed. MDC will do fine with top end talent around him but he'll never drive play. That's why he's not a center. Barzal has the potential to do that. He's built like a horse already too, MDC (as stated in the article) is going to have to hit the weight room hard as well as work on his skating.
Lastly, don't really think JVR fits on the Isles right now and he actually seems to be in a great spot with TO. Good veteran, still young, and going to be surrounded by some energetic rookies. I think he'll flourish in his role there and I don't see why TO would want to move him.