I think that Dortmund will have a tougher game than Bayern Munich next week. Because their opponent is Leverkusen which is a tough one than Leipzig this season. Leverkusen are at the third position in the standings right now. However, this still doesn't matter too much for Dortmund if we take their recent effort into account. For example, Freiburg were also one of the top teams in the standings but Dortmund still didn't care about it and destroyed them. Maybe the Leverkusen game would be a competitive one but Dortmund should be winning this one too.
I still remember the first game of Dortmund vs Leverkusen in this season. Back then Leverkusen was the stronger team in my opinion and Dortmund was pretty lucky that they have won that game with 4-3 in the end because Leverkusen was still ahead 3-2 in the 70th minute. So maybe we can expect such a close and exciting game again. I don't think that you can compare that game to the one vs Freiburg because it is a pretty big surprise that Freiburg is at the top of the table and if they have a bad day like they had in the game vs Dortmund 2 weeks ago they usually have no chance against top teams. So i expect that Leverkusen will be a tougher test for Freiburg.