Both Jack and Johnny were substantially better with each other than apart. When Jack wasn't with Johnny he was usually playing with a kid or an underperforming vet in a depth role, so it's not surprising that he popped more on the top line.
I also haven't seen it mentioned here but Jack fractured his ankle in November and took a month or so after returning to get his wheels back. So that will change how this year's numbers look. Maybe don't take the analytics too seriously on that. He's always been an inconsistent player in general so a big drought might have happened anyways.
In Columbus we expected a big yearly disappearing act from Jack. I like this move for the Rangers though because going deep in the playoffs always requires a bit of luck, and you might just get a top line caliber forward out of Jack for the whole run. That or nothing.
But when he's on, he's a top line forward, unquestionable top line skill. He can do everything when he's on. The most frustrating thing about his game, which he's improved at lately, is the first pass after the zone entry. Jack can pass and he can gain the zone with ease with his speed, but he would often overthink his first pass after gaining the zone or make some dumb drop pass to nowhere. He's not Panarin. But you can get a lot of value out of him if you can get him to simplify, the basic skills are good enough to put up points without any magic required.
Playing with good players like Zibby and Kreider should be good. I know they're not 5v5 play drivers but Jack can handle a lot of zone entries and they're good enough scorers that you hope he'll just make a simple pass out of respect for what they can do. It's when he tries to make the pass of the year that things go off the rails.