I think Lewandowski just about shade it with his performances in big matches. But I do remember lots of people saying Dortmund is now a selling club after Gotze, and so many news paper reporting the big exodus that never arrived. Instead they use the money wisely and built an even better side. Michitarayan is like a like for like replacement for Kagawa, a proper goal scoring midfielder. Aubameyang provides much needed depth to take pressure off their only CF last season. They even strengthened their defence with Sokratis and sold all their deadwood.
I think Gotze will be a top top player, but he is going to stagnate a little at Bayern.