The rankings this year are pretty varied. Celebrini is the only consensus pick. Demidov is pretty close at #2 but plenty of guys have him going later. That's where I look at Helenius and can't pinpoint where he might do. After Celebrini, he's arguably the next best center - right there with Catton. But say you're picking at #2 or #3, I don't know how you could pass on Demidov of Levshunov. It's really tough pegging the top 10 right now. Very reminiscent of 2006, where it was Eric Johnson as the clear #1, and then you had Toews, Backstrom, Staal, and Kessel at 2-5, and you could legitimately take any player in any slot (certain a center at any spot. I think Kessel was going #5 but still).
What's your take on Dickenson? He's climbed the ranks a bit and looks to be at the 6/7/8 range, but I don't have a ton of hype over him. Granted, it's mostly from highlights, but watching them, I never would have pegged him as a top-10 prospect. Unless I'm just completely off. He looks like he would develop into Dumoulin based on scouting reports. Couldn't tell if it's an indicator of a weak draft or if I'm just completely underrating him.
He'd be a great pick. As a RH RD, I think you could be looking at a decent Karlsson replacement. Not in overall skill set obviously but an anchor 2nd pairing RD until Letang retires. I imagine by then we'd know if he could be a potential top pairing replacement.