It would be disappointing if this Leverkusen team doesn't get second spot this season, their squad seems pretty clear as the second best in the league. You could say Dortmund can compete in terms of the first XI, but Leverkusen have built a fantastic overall squad that really puts them ahead of the competition. Just going through the positions, they are pretty stacked:
CB: Tah, Tapsoba, Hincapie, Kosonou, Stanisic
RB: Frimpong, Arthur, Stanisic
LB: Grimaldo, Singraven
CM: Xhaka, Palacios, Andrich
AM: Wirtz, Hofmann, Adli, Amiri, Hlozek
ST: Boniface, Schick, Hlozek
And that's with keeping a positive cash flow this transfers season. Maybe one or two more may leave (Hincapie and Amiri) but even then that is a decent balance.
The only weak area where you feel they don't have quality is GK, Hradecky should have been replaced ages ago and isn't reliable. Other than that CM looks a bit thin since there are only 3 defensive minded midfielders for 2 positions they hold. Picking up Stanisic on loan with Grimaldo on a free were great deals.
Let's not forget Xabi, who has made Levekusen look really impressive since taking over.
I really hope they can accomplish something, either a DFB Cup win or a deep run in Europe (quarters or semi) to have accomplished something because this squad will likely be gutted next season. Wirtz, Frimpong and Xabi will surely leave along with one of Tapsoba or Kossonou. Maybe there would be hope of them staying if they can do something great this season.