Gudbranson was always going to be a project. I said it at the time of the draft (having followed him closely when he played for Kingston), but he was the rawest of all the top picked defensemen that season. Guys like Fowler, Gormley, etc. were all more polished players at that point in time. Gudbranson was more an unfinished product.
He was drafted high because the package, if he put it all together, was very impressive. Great size and physicality, good mobility for a big guy, good in his own zone, good outlet passer, and has a hard (albeit inconsistently accurate) shot.