The third line of Marchand, Lundell and Luostarinen doing that good is 100% abnormal. The line put up solid second line kind of pts. On weak scoring teams, they put up top line pts. In the regular season, they were not this good.
But it shows how solid the team is built and as everyone knows in hockey some players are better built for the playoffs (stamina and grit to grind out 7 game series over and over again) than regular season matches which are one off games where half the teams are crap. Talented floater dudes do well in reg season. When playoffs comes and all teams making it are decent or elite and the players go balls out trying to win and crush guys into the boards that's when the players who play a non-physical game often get neutralized (guys who dont like getting hit or stand in front of the net getting checked, wimpy pass focused players etc...)
Talented teams like Oilers rely on PP to gets goals too. When the PP opportunities dry up (like yesterday with no penalties which is rare), so does their scoring as their even strength scoring may be nothing special. Florida can dominate at even strength or PP.
Marchand is still a good player. He's old, but having him on a third line adds a lot since third line checking players dont have guys like Marchand who can do a bit of everything. On other teams, he'd probably be a solid second line player. Maybe even still top line on shit teams. But on Florida they put him on third line.