In what way?
Their first choice attacking midfield, Mkhitaryan, Kagawa, Reus, looks really strong (at least with Mkhitaryan's and Kagawa's current form - Reus I believe is still isn't at his best yet), but behind that they fall off rather sharply.
Castro couldn't replicate his Leverkusen form yet, Hofmann (kind of a Müller light, since he looks quite average but seems to be able to compensate for it with football intelligence) is a good and very efficient sub imho, but individually not good enough to be a long term replacement, Januzaj is still your typical youngster with the lack of consistency that comes with it and he also has to adjust to a new league and coach, Tuchel might be the right guy to get immediate results from him, but to me it seems just as likely that Januzaj will be behind Hofmann.
At #8 it looks somewhat similar. Gündogan is looking better and better again, behind that they have Castro, who hasn't impressed yet and then comes who? Sahin isn't dynamic enough to be a great player here. Reus and Mkhitaryan could probably play that position, but then they'd be missing in their normal position.
The #6 is probably where their depth is the best. Weigl looks like a perfect fit and Sahin already impressed in a somewhat similar role. Only the Turk has been injured for ages now and afaik is making little progress.
Bender is simply too limited for the football Dortmund want to play now. I think he's a huge liability for their build up and I don't seem him starting any remotely important matches as long as they stick to their system/style and either Sahin or Weigl is available.
Leitner is just a sad story, looking more and more certainly like a wasted talent. Afaik Dortmund wanted to get rid of him this window, but for whatever reason a transfer didn't happen. Unless he undergoes some miraculous development I don't think he will play a lot of minutes (if any).
fair enough, and i second the notion that castro has, so far, been the most underwhelming addition and remains a piece of work, quite surprisingly - though i didn't really mean the players' current availability, form and fitness, but rather the assembled midfield department as a whole. what i see is an abundance of highly versatile players, so the depth of the squad lies, first and foremost, in its seemingly endless variability in formational and tactical tweaks, and to a lesser extent in its overall number of players. as to how much of a dangerous approach this can possibly turn out to be depends as well on unpredictable, external factors - from unforced injuries to lengthy bans or whatever - so i can see where the doubts on the squad's depth are coming from.
btw, i may not have been the only one too optimistic when it comes to the ongoing drama that is nuri sahin's prolongued (non-)recovery, which - if true for the time being - leaves us indeed very light on such a crucial position, with a 19-year-old, yet amazingly composed newcomer in julian weigl as our only genuine, tuchel-approved #6 - but then again: if we're complaining about sven bender and castro/gündogan as our 3rd and 4th options, plus another 5th and 6th option in two young german internationals who go by matthias ginter and moritz leitner - as useless and out of form as we may tend to think of the latter - then that squad looks obscenely good to me, as i can also do the same for every single midfield position:
#6: weigl, [sahin?], bender, castro, gündogan, ginter, park
CM: gündogan, castro, leitner, weigl, (kagawa, mkhi, januzaj)
AM: kagawa, reus, januzaj, mkhitaryan, castro, gündogan, leitner
RAM: reus/mkhitaryan, hofmann, (aubameyang, castro, leitner, piszczek, durm)
LAM: mkhitaryan/reus, januzaj, hofmann (ramos, castro, leitner, durm)
of course we'd probably be losing quite a bit of our current momentum if we had to miss out on two or more regulars of our so-far-shining offensive line, though i for one can't but feel like it'd need the absence of at least three or rather four midfield-rotation contenders to
really get me worried about most of our matches - say if we were to miss out on two out of weigl/sahin/gündogan/castro AND two out of mkhitaryan/kagawa/reus/auba - though even in that case we could as well switch to a more stable formation than the usual 4141/442, like a 4231/442, thus allowing us to field a somewhat proper, decent first XI and scrape points - which is, by the way, exactly what tuchel excelled at during his time as manager of mainz, where he used to work with a similarly thin, though decidedly less talented squad which he was able to push beyond their suggested limits, and continuously so.
plus, and god beware, if in fact half of our midfield department were to be ruled out, we may even have to temporarily bench some of our upcoming youngsters like maruoka, gyau, passlack or burnic