If I were to add it in my games, I'd take a safee option of either 1.5 or 2.5 since giving Dortmund a straight win can be tricky.
I agree with you about how Dortmund have been operating since they lost that opportunity of winning the league title on that final day of the season, I think that was 2 seasons ago, they have been on my bad book of teams that are very good at disappointing gamblers. Although this season the only thing they are good at is giving up to 3 goals in a game, with their opponent being Heidenheim I don't still see any reason to give them a straight win and we should be careful with the bigger teams this week because we have the craziest champions league games so some of the bigger clubs might fail to even score more goals or win a game rather they choose to settle for a draw just to be ready for the UCL games ahead.
In this encounter between Dortmund vs Heidenheim, I don't mind if Heidenheim is a newly promoted side, I have the feeling that it will be both team score game and this option (BTS) will happen in some of the games involving the bigger clubs around Europe.