Dunno. I was very critical about the whole KdB/Draxler thing, but I understand why it happened. It was a okay solution in a difficult situation.
The bigger issue is, that they have a very average squad. Three players on CL-level (Naldo, Gustavo, Rodriquez) and three decent ones(Vierinha, Kruse, Draxler). The rest of the team is somewhere between euro-league and midtable. They also don´t have any promising talents (with the exception of Draxler), so they will struggle to improve. Didavi is another okay player. 26 years old with a long injury record.
In the end it depends on their ambitions. He might improve them, but they won´t compete for the CL with players like him. They did similar transfers in the past (Jung, Träsch, Schäfer, Dante, Caligiuri). Bundesliga proven and solid, but not good enough if you want to finish top4 (or even top7)