Even though Boston can close out the series with a victory here leading 3-1, I'm not convinced the Bruins are the superior team.
If you discount a late empty net goal, every game has been decided by one goal. The Bruins have managed to win three of those four games. If the Hurricanes didn't blow a two-goal lead in the last game, the series would be even at 2-2 and this betting line might be different. 
Yes, it's a blow that the Hurricanes lost rising star forward Andrei Svechnikov. But he also had missed time when the Hurricanes met the Capitals in the first round last season. The Hurricanes won that series. 
The Bruins are not unscathed. Their leading scorer, David Pastrnak, has not played in the last three games and starting goalie, Tukka Rask, opted to leave the team.