I don't think he's "overrated" in the sense that he's an incredible puck moving defensemen already at such a young age. It all seems very natural for him to bring the puck up the ice and create plays and make things happen with his fantastic vision.
Having said that, on the defensive side of things, it's a little bit of a tire fire. I won't judge solely based on his +/- which is by far the worst on his team, but just by watching him play, you can't help but noticed how lost he is in the d-zone. We're not just talking about blown coverage either, we're talking full on basic defence here. It doesn't help the the rest of the defence in Vancouver isn't particularly good, but you can't help but think that a coach needs to spend some serious time with him to make sure this doesn't become a long term problem.
Yes, he's young and he makes young player errors, but he's a jewel and you don't want to waste his talent long term.