That last point strikes me as odd. You could say the same thing about his offensive game, or just about any other area.
Oddly enough, I think the biggest limitation currently holding back his offensive game IS his defensive game-- He spends too much time hemmed in his own end unable to push things back the other way. Once he has the puck entering the offensive zone, he's very effective (despite occasionally selfish/tunnel-vision play). The ice just isn't tilted in that direction when he's on the ice nearly as often as you would think he's capable of.
On top of that, expecting him to dramatically improve his offensive game sounds a bit unrealistic/unfair of an expectation to me. It's possible, but it's not something I'm banking on. If he tops out at a 60+ point pace for most of his career (which he's already pretty close to doing consistently), that's pretty fitting for his talent level. Meanwhile, his defensive game seems like it should be at a level dramatically beyond what it is right now, I would most expect that focus to bare results, and it would probably help his line's overall effectiveness more than anything else, IMO.