Pacioretty broke a 2-2 tie at 12:18 of the second period, 26 seconds after Trocheck scored on a wraparound.
"We tied it at 2, we have all the momentum and it seems like we just feel like we're going to coast the rest of the way," Trocheck said. "It's a 2-2 game against one of the best teams in the League. Got to come out that next shift, that's one of the most important shifts of the game, we get outworked on that one. Every goal we gave up, they outworked us."
Stone gave Vegas a 1-0 lead at 2:15 before Hoffman tied it 1-1 with a power-play goal at 16:22.
Stone put Vegas ahead 2-1 at 1:41 of the second period when he carried the puck from his end, got around defenseman Mike Matheson and shot under the crossbar.
Before Trocheck tied it 2-2, Fleury stopped Brett Connolly on a penalty shot at 6:40.
"I thought [Fleury] made a couple of big saves, including the penalty shot," Golden Knights coach Pete DeBoer said. "Those are momentum-changing moments in the game, and I thought he really gave us a big save there and some momentum that shifted our way. And then I thought the group dug in in the second and third and really started to impose our will on the game and got rewarded for that."