Morgan Geekie scored, and Jeremy Swayman made 27 saves for the Bruins (30-31-9), who have lost four in a row (0-3-1).
“They came in waves. They played well. That's a testament to their team. It's our job to combat whatever they bring to us, and I thought we did a good job of that,” Swayman said. “We just didn't get the results.
“We can't let things snowball and worry about the past because we can't control it, and that's a message that we hope to get across to everyone here. We just got to keep moving forward. We just need to keep moving forward because that's all we can control and just keep pushing for that playoff spot.”
Dorofeyev gave the Golden Knights a 1-0 lead at 9:19 of the second period with a power-play goal, beating Swayman with a snap shot from the left circle off a touch pass from Eichel.
He then made it 2-0 at 19:10 with a snap shot from the slot off a face-off win.
Howden pushed it to 3-0 by roofing a Karlsson pass on the rush at 5:47 of the third period.
Dorofeyev completed the hat trick to make it 4-0 at 10:21, finding a loose puck in front and tucking it away with a backhand.
“He's just a natural goal-scorer,” Hanifin said. “If he gets an opportunity and a Grade-A chance, he's going to score and capitalize, and getting players like that is pretty rare. So, we're happy to have him here.”
Barbashev made it 5-0 at 14:24. Eichel raced ahead of the pack and found Barbashev with a backhanded drop pass from the goal line for a one-timer in the slot.
“I'm happy that we didn't take our foot off the gas and went for that third and eventually the fourth and so on,” Karlsson said. “We need to keep that mentality going forward as well.”