I don't know the stats off hand, but I'm willing to bet there's been significantly more goals scored against with him on the ice then he's scored during that same time span.
For that reason, I want nothing to do with Kessel.
Give me Eriksson for a prospect + 2nd pick versus Kessel which will likely cost a good prospect + 1st round pick + more
48.9 GF% between 2011 and now. So he's below even, but I wouldn't really say significantly, especially when you consider how bad Toronto's been in that time.
EDIT: Kovalchuk was 47.7% in his four years before he became a Devil, so it's not like the idea is unprecedented. But still, for the way the Devils are constructed right now, I don't think Kessel would make me drop 15+ spots in this draft. If we were remotely competitive, I'd do it in a heartbeat. To go along with what I think you were getting at, Kessel probably shouldn't ever be "THE" guy on a team. Surround him with good players and let him do his thing.