A few things to remember
1) Dupuis and Kunitz looked great at the start of last season(minus Kunitz's miserable first week) and slowed down towards the end of the year. I don't think enough people put enough stock in how ahead THAT LINE was over the rest of the NHL. They practiced together non-stop. Other players didn't play/practice, played overseas, played in the A, etc... They were more in-sync than their competition. This year, the have no head start: everyone had training camp, practices, etc... I don't expect Dupuis to look like a great top-6 player at all this year. There's a little thing called variance. It's more likely that Dupuis (and Kunitz, as far as goal scoring goes) experienced a weird bout of statistical noise in a shortened season than it is that they drastically improved in their mid-30s.
2) On the flip side of that: Glass sucked last year, but his shooting % was unsustainably low. So that he'd score more this year shouldn't be a surprise. I'd hesitate saying too much has changed, yet, but he's certainly passed the eye test through the first 4 games.