I'm not an expert, just a BVB fan. So take this FWIW.

First, I think Pulisic was better last season than in 2016-17. However, I think many expected him to make a huge leap, and his progress is 2017-18 was more modest. For most of Bosz's tenure, despite being played in a more defensive role, Pulisic was Dortmund's most aggressive and effective attacking player. He didn't have goals and assists to show for it, but he was very influential, especially in the early part of the seasom. Stöger played him in a more advanced role, and the stats started to more closely reflect Pulisic's impact. I think his assist stats were bolstered by having a more effective finisher than Aubameyang on the end of his crosses.

Of course, because of his growing influence and the absence of Reus, Pulisic drew a lot more attention from opposing defenses. I think the pressure took a toll on him, physically and mentally. The return of Reus and Maxi Philipp and the emergence of Jadon Sancho helped lighten his load. If those guys stay healthy and Dortmund pick up a solid striker, I think we'll see Pulisic's production tick up this season.