It definitely is a team stat, but Hanafin has been amongst the worst +/- players in all but one of his five NHL seasons, on two different teams. I'm not sure exactly how he's deployed, but I don't think he ever gets the toughest minutes. He's always had a Slavin or Brodie ahead of him to eat big minutes against the oppositions best.
I like Hanafin, but not enough to give up what it would likely take to get him. I also really like the way this team's defense is shaping up for the future. Hronek, Seider, Johansson and Wallinder all have the potential to be legit top four defensemen. Any trade for a Hanafin caliber / aged player would likely cost one of those pieces, plus. I'd rather hold on to what we have for now, and make a trade or free agent acquisition like Hanafin in a couple years when we're actually ready to be competitive.