Chelsea has now three opportunities to play against teams that are not in top shape in the Premier League. Perhaps this win against Dortmund now gives them a push and they can improve. If they started a winning streak now of three consecutive games, they would afterwards host the game against Liverpool and that could be their final chance to keep a realistic probability for the qualification for the international ranks in the table. I doubt that they can still make it 1-4, but if they win a lot of games the Europa League could still be achievable.
Usually, Chelsea will fight and struggle when meet a strong team and be careless when meet a weak team. By winning on the champions league last night, It does not mean Chelsea will able to win the next match versus Leicester and Everton. As I know, Chelsea is seem not focus on premier league, maybe they searching another way to keep it strong by focus only on champions league.
You are right, seeing Chelsea's potential in the Premier League is very difficult. Especially with the capital points they have and the remaining matches it will be increasingly difficult to get past the club above them. They do look to be chasing the Champions League, but even then they are still in the last 16 while the opponents they will face will be much stronger. Chelsea's Premier League play has been terrible and this season Potter hasn't produced great results against Premier League clubs.