This is what I see as well. He doesn't have the offensive IQ or high-end offensive skills to be a real threat to score by the looks of things. However, if he can exit the zone with the puck under control and skate out of danger in his own zone (both of which he appears to do quite well in fact), that is a very valuable skill to have. I personally don't see a top-pairing guy that can also play on your PP (even a 2nd PP to be honest), but I see a guy who could be a 2nd pairing guy who chips in with 15-20 points a year.
To compare him to our current Dmen, he is almost a mix of Nurse and Klefbom, without Nurses physical play, or Klefboms bomb shot (at least before his shoulder injuries). He has better wheels than Nurse, and seems to have a slightly better idea of what to do with the puck on the rush than Nurse. He doesn't have Klefbom's shot, but his superior skating and similar or slightly better size should allow him to cover more defensive territory than Klefbom does.
I think it is really going to boil down to his defensive awareness and ability to play sound positional hockey, as it does for many dmen I suppose. But with Broberg, his physical attributes are so good, that if he can at least be average positionally, he can make up the rest with speed + size.