You have to remember that he is an 18 year old defenseman which is the hardest position to transition from, coming over from international ice that hasn't played the North American game aside from tournaments. Also with Ristolainen there it gives Dahlin some time to adjust and I think will be better for him down the road. I am tempering expectations off the bat.
I think he takes a similar path as Hedman, but hits his stride a bit sooner. 30 points wouldn't be a bad first year for him.