Alcacer hasn't been, and likely will not be Dortmund's 1st choice striker. He starts on the bench more often than not. Reus will play up front, or Favre will play with a 'false 9' type forward.
I like Götze and was happy to see him re-discover some form this year, but Brandt is a younger, more mobile, more skillful player, who really hasn't lost any of his star power. He's only just getting started.
I agree that goalkeeping needs a bit of a look, Bürki is much improved, but still eratic. The problem in defence last year was more to do with injuries, the coach wasn't putting Weigl in there originally for the fun of it, it was a desperation move. Akanji and Diallo are a very good pair. Getting a better 3rd choice would be advisable though. But the summer window has only just started, I don't think Dortmund are done. Hazard, Brandt and Schulz are big upgrades for the squad and should help Dortmund push on, so we must be seeing different things in these players! They are more than 'decent' deals.