Champions League games will happen by February next year it cannot be the reason that one will lose match of today.
Dortmund might also not do better next year because in January open window it is obvious that many clubs will be coming for Billingham and he will likely leave the Dortmund team which will be a very big blow to them
I would even say that Dortmund has to many points at the moment given the performances that they have shown in a lot of games. Just look back at the beginning of the season. In the very first match against Bayer Leverkusen Dortmudn was definitely not the better team but managed to score a lucky win with 1-0 even though Leverkusen had way more better chances to score. In the second match day against Freiburg Dortmund was well deserved 0-1 down until the 77th minute before the goalkeeper of Freiburg made a huge mistake and brought Dortmund back into the game basically out of nowhere. I think Dortmund can be pretty happy with the amount of points that they are having.