I didn't start following youth hockey until Sakic retired and the avs finally accepted that we needed to rebuild, so I can't say on Pronger, but I can certainly believe it just based off of what he became in the NHL for St Louis. I'm in full agreement that we (and draft analysts) should drop the positional constraints when discussing this order of prospect; but hockey is a conservative sport that can be very stuck in its ways. And comparing forwards to forwards & blueliners to blueliners is definitely one of those things that folks are oddly resistant to.
Even more than Dahlin's highlights, which are stupefying, what has blown me away so much about him is the poise & control with which he played whenever I caught his SHL games. He didn't get any points in two or three of them, and he only got one point (maybe two) in a couple of the others, but even in those games the talent & creativity just smacked me in the face and it was obvious that they allowed him to do things that hockey players, even awesome hockey players, generally can't do. Even though he's clearly still figuring out just how dominant he can be, he showed that he already had a pretty good feel for how to use his gifts to control the game when he was on the ice...and I'm genuinely a little bummed that the Hawks didn't get him, despite them being divisional rivals, cause if they had, I could watch him live on a regular basis
Blueliners being less predictable is certainly a factor to keep in mind when assessing Rasmus, and; combined with the more unprecedented production McDavid had in his favor; is why I would vote McDavid as a prospect over Dahlin as a prospect. But I do think that their talent is comparable and on a tier of their own from the other franchise-caliber talents. And it helps that the league has been getting so much better at projecting & drafting blueliners, so I'm not as anxious about Dahlin's development being mishandled as I would have been if he was being drafted 15 years ago.
Production is important because you don't get style points in hockey, but production is something that I worry about more on a pass/fall basis. Meaning, as long as a kid has shown that he can produce well when put in a role to produce, I'm not as interested in quite how well he is producing while still developing. As long as that base level of production that I think his talent warrants, is reached or has been in the past, if current circumstances aren't favorable to producing up to his talent, then that's all I'm really worried about. Cause like I said I prefer for talented kids to err on the side of risk when they are still developing, learning when to play it safe comes with experience and can always come later, but there's no better place to hone your creativity and learn how to pull off the risky, than the youth levels and your pre-NHL days.