Playoffstatus.com says they've played the hardest schedule to date and have the easiest remaining schedule left, based on the winning percentages of those played versus those remaining. Maybe that has something to do with it.
Maybe they've learned that winning the President's Trophy is pointless and aren't giving 100% knowing all they need to do is qualify. I don't watch them often so I don't know why they are "underperforming". But with that lineup, and only 1 win away from 3rd place in their conference, I feel pretty certain they'll be there come playoff time.