I still think they have a pretty good team and yes of course Bayern will be favourites for the league but Dortmund will probably be their main challengers
.............................Aubamyang...........................
Reus........................Gotze.......................Schurle
...................Bender..............Weigl......................
Gurreriro.......Sokratis.......Ginter...........Piszczek
...............................Burki..................................
Is a pretty good team I think - and they have plenty of quality to back it up as well
Wedenfeller, Bartra, Durm, Sahin, Kagawa, Pulisic, Dembele:
Bonmann, Bandowski, schmelzer, Castro, Leitner, Rode, Ramos
And thats presuming Blaz and Subotic go...
If they stay largely injury free to key players I can see them doing very well in Europe this year if they line up something like that
Imo Ginter won't play as CB, Bender won't play in midfield.
I think Sokratis, Bender and Bartra will be equals for the CB spot, Tuchel will probably pick a pair (if he doesn't use a back three) based on tactical considerations (Sokratis = destroyer, Bartra = play making, Bender = something inbetween).
Schmelzer will probably have a head start, because Guerreiro is new to the league and will miss a lot of the pre season, mid term I can see a similar deal as on the CB position, Schmelzer for a more defensive role, Guerreiro for a more attacking approach or WB.
Piszczek seems a safe bet for RB right now (Durm might be prefered as RWB, with Piszczek as RCB).
CM will probably be Weigl + two out of Rode/Kagawa/Castro/Götze (assuming a 4141)
On the "wings" Reus will be a starter, otherwise it'll probably be between Schürrle/Götze/Dembele, for the first team.
Also afaik a Götze deal isn't official yet and while Schürrle seems likely thus far we only know that the player is willing but Dortmund and Wolfsburg haven't reached an agreement.
Dembele, Bartra, Mor and Merino could turn out either way, so it's hard to make predictions about their strength next season, though obviously it seems likely that they won't be as good as before losing the trio.
edit:
Zorc: "utter nonsense, the deal is not done"