Perfect storm, Dortmund make their players rise above their level, a case of "greater than the sum of their parts". Many players go to Dortmund and with the ethos of the club and style of football makes attackers especially look levels above. See - Kagawa, Mkhitaryan, Goetze, Gundogan, Auba, Lewandowski, Sancho, Reus etc.
Can he replicate that elsewhere? I think so but maybe not to the same insane level. The Dortmund teams are always great at getting the most of their attacking talents so going to another team I feel, if they work with him, he will continue to improve and maintain this freakish consistency. There is a risk (with all players) this might not be the case but what he is showing currently is performance levels far above Lewandoski and Auba, who are their two best exports who have done it in other leagues etc.