I also read the rumor briefly but I didn't explore it in more depth because it was still not really official. But if that could really happen to Dortmund, I would also be very worried about Dortmund's condition because Ten Hag is not a coach who has many unique tactics so the development that Dortmund itself will get may not be much different from what they are currently experiencing. And at this time I also wonder if there is no one else that Dortmund can look at other than just Ten Hag, because Dortmund really needs a coach who is experienced enough to develop a team when it is in a slump like now.
I agree to your point, Ten Hag isn't a coach that will successfully see a team through development and get them good success, I know some persons may want to argue that at Manchester united, he was able to achieve two trophies and that made him appear like a coach would can be addressed as a good one but if we look at his performance in depth we get to see that there's no tactical fluenc, it's just basically survival pase he's been going with and probably looked like he just got lucky and the Bundesliga has got a very fiercey approach that needs beyond just survival strategies if you must maximise results from the German Bundesliga.
I feel you are talking to me directly because i'm one of those to argue with you that Ten Haag is not as unproductive as some of you are saying because he made efforts to change the football dynamics at Manchester United but he didn't get all the support he needed to excel at the club namely from the players precisely. It was only the club that gave him a small benefit of doubt after he won the F.A cup for them but yet it still got to a time when they couldn't keep him any longer which resulted in the club sacking him. Currently now, is the club doing any better after Ten Haag's sack? No, they ain't.
Borussia Dortmund is a club that already has tactical players so they literally do not need a tactical coach before they can perform excellently. The club has been in the business of producing young talented players and afterwards, sell them off to other European teams so how would such club excel when they sell off most of their relevant players and leave behind the average ones. Until they allow those young stars develop very well in the team and bring forth trophies to the club, they might still be faced with difficulty in standing out in the Bundesliga so i don't think their problems is associated with being as a result of lack of tactical coach.