This team has 6 guys (Seguin, Marchand, Lucic, Horton, Krejci, Bergeron) capable of scoring 25+ goals. Also, Seguin put 29 in the net at the ages of 19 and 20... he's only going to get better and better every year. Not even close to his prime. He may be that "elite scorer" and I wouldn't be surprised at all if he hits 40 in a near future season. On top of all those guys there's Peverly, Kelly, and Caron. We saw 20 goals from Kelly last season, Peverley is capable of 15-20 if healthy, and who knows what Caron will be able to do.
On top of all of this, the Bruins have one of the best defenses in the league.
Signing/aquiring a big name like Nash or Parise isn't something necessary for this team at all. With the young core of players the currently have, and the players coming up through the system (who will hopefully live up to their hype), this team should be set for a while to come without the aquisition of a big name goal scorer.