Borussia Dortmund use to be very consistent on there Bundesliga then but now a lot of things has changed about them, though Borussia Dortmund is well known in terms of generating a good players because the above listed names are currently doing very well on there current clubs.
Borrusia Dortmund have to spark their shining stars because that's the only path to bring them back to winning ways. It's never going to be easy for them because the board made huge mistakes in previous seasons. It's never been an easy road for Borrusia Dortmund, they sold all the potential talents and left with nothing currently. However we have nothing to worry about because they're always lucky to have in possession incredible young players. 
There is nothing wrong with Dortmund because selling star players has become their tradition this season. Look at the transfer market this season, they have sold Niclas Fullkrug to West Ham as their step to recruit other young players who will be polished into star players. Management always cashes in on players if the player gets big attention from elite European teams.
Apart from that, management and talent scouts always succeed in finding the right replacement for every gap left by players who leave. Will Maximilian Beier be successful in being recruited by Nuri Sahin because he thinks this young striker will be right enough to help them this season?