It is true that it is very likely that football fans throughout Germany will support Dortmund in the UCL final, but facing Madrid in the final is not an easy thing, especially since Madrid is always the winner in every match in the UCL.
Tomorrow Dortmund will face Mainz, this is quite an important match for Dortmund, don't let Dortmund's main players get injured in this match, Terzic will definitely field Dortmund's reserve players in this match.
Yes, it won't be easy to beat Real Madrid, but we have to remember how Manchester City gave an unexpected surprise last season and this could be Dortmund's motivation to be more enthusiastic about winning the Champions League title and most importantly, maintaining the quality of players is now much more important.
I agree with you that Terzic will definitely prioritize the UCL matches and will give the main players a little more rest even though the results are bad in the Bundesliga. The most important thing is that the UCL will be Dortmund's priority.