There is absolutely nothing wrong with the prospect of drafting Hanifin, but like 101 said, at this point in time it would be incredibly short-sighted to ignore the recommendations of the scouting staff that has watched these kids all season long and to disregard their rankings.
The Leafs literally could not lose out by drafting any of the Big Three in Strome, Marner, and Hanifin. Any one of the three would go first overall in many of the drafts from the past twenty years.
Nitpicking over which player the Leafs selected is illustrative of the quality and depth of this year's draft class if anything.
So much this. Hanifin putting up the kind of numbers he did as a 17 year-old against NCAA competition was amazing. Dylan Strome's numbers were a complete head-turner, even if he did have Connor McDavid as a teammate.
But to put what Mitch Marner did in context...he played on London's first line, and got the opposing team's best players matched against him and his line night in and night out. In spite of that, here's how his draft year stacks up with the draft years of the top drafted forwards from the last 10 drafts:
(includes regular season & playoff totals)
Mitch Marner: GP 70, G 53, A 89, Pts 142,
PPG 2.02 (2015, 4th overall)
Sam Reinhart: GP 73, G 42, A 86, Pts 128,
PPG 1.75 (2014, 2nd overall)
Nathan MacKinnon: GP 61, G 43, A 65, Pts 108,
PPG 1.77 (2013, 1st overall)
Nail Yakupov: GP 48, G 33, A 41, Pts 74,
PPG 1.54 (2012, 1st overall)
Ryan Nugent-Hopkins: GP 78, G 35, A 82, Pts 117,
PPG 1.50 (2011, 1st overall)
Taylor Hall: GP 76, G 57, A 84, Pts 141,
PPG 1.85 (2010, 1st overall)
John Tavares: GP 70, G 68, A 57, Pts 125,
PPG 1.78 (2009, 1st overall)
Steven Stamkos: GP 70, G 69, A 47, Pts 116,
PPG 1.65 (2008, 1st overall)
Patrick Kane: GP 74, G 72, A 104, Pts 176,
PPG 2.37 (2007, 1st overall)
Jordan Staal: GP 87, G 38, A 46, Pts 84,
PPG 0.96 (2006, 2nd overall)
Sidney Crosby: GP 75, G 80, A 119, Pts 199,
PPG 2.65 (2005, 1st overall)
Marner was a more prolific scorer at the CHL level than eight out of the past 10 forwards who heard their names called first at their respective entry drafts. The only two players who did better are Patrick Kane and Sidney Crosby.
So, being disappointed that we ended up with Marner in any way, shape or form is flat out nuts, IMO. The kid could easily be the best forward this team has drafted since taking Lanny McDonald at 4th overall all the way back in 1973, or Vincent Damphousse at 6th overall in 1986.