I agree with you. Dortmund may want to finish their work in the first leg already. And we could really see them doing it by a big score difference. Rangers are one of the best teams of the Scottish Premier League. But there are not many strong clubs there so it is totally normal. Dortmund are a world-class team compared to them and they shouldn't give any chance to Rangers in this.
I would be very surprised if Rangers manage to get a tie against Dortmund. Dortmund are a very strong team compared to Rangers. Of course the Rangers will fight and try to surprise, but I have some doubts that they will be able to do it.