I see Batherson as a poor man's Mitch Marner who would flourish feeding a scoring centre like Norris; but on a very good 2nd line. He has an average shot and has very good play making skills but needs to work on his defensive game. Nothing in his repertoire suggests he would be a 1st line player on a good team.
I think there is a distinction between being 1st line cornerstone player, versus a 1st line player. Marner is an absolute cornerstone guy who perhaps finishes top 3 for the Art Ross. To hold 1st liners to that standard, is basically saying there are only 20-25 1st line players in the league, rather than 90 or so.
As to playing with a superstar, do you mean BT or TS? Not sure either is an elite producer yet that is dragging Batherson's production along, although Drake is definitely benefiting from PP time.
That said, he is arguably the best puck mover on the PP, so he certainly belongs on the first PP Unit IMO. While not scoring in droves, the 1st PP unit has looked terrific of late. Jimmy helping there, but loving some of the cross ice passes between Jimmy and The Drake.