I agree about the injuries and some of the reckless penalties, but I think you're downplaying his offensive potential and chemistry with Matthews.
Offense-wise, he wasn't exactly playing with superstars for most of his time in Detroit. How many goals can you get with a very young Larkin, Athanasiou, Nyquist, etc? When he got to Boston, you really saw him take off. Likewise, although it took some time, with Matthews, he really started scoring, and I expect that to continue next year. I think the chemistry is real. Matthews's insane goal scoring was, at least partially, influenced by his teammates. We've put a bunch of guys with Matthews over the years and, with the exception of the "stars" like Marner and Nylander, Bertuzzi and Domi are the best role players I've seen mesh with Matthews since this era began.