The Sens finished below Buffalo because they got off to a horrendous start and dug themselves a hole so deep they couldn't catch up. For the first couple of months, they would record blowout wins followed by close losses, which explains the goal differential.
Right now, this team is playing New Jersey Devils hockey as well as the Devils ever did at the height of their powers. They clog up the middle, they block shots, and they force mistakes. But they also have one ridiculously talented line that can be counted on to get them leads they can protect. The other three lines don't have as many points because they're mainly concentrating on playing good shutdown hockey, and they can do that thanks to the Cash line always giving them a lead to sit on.