I think it is rather the exception than the rule that a team which is performing bad in the domestic league is one of the strongest teams in the Champions League. Yes I know that now some people will come up with examples, like Sevilla and how they won the Europa League last season when they were so bad in La Liga. But where is Sevilla now? They finished their Champions League group with 2 points out of 6 games and got destroyed in almost every game. There is a correlation between the overall performance of a team in the league and the other competitions, but yes there are exceptions of course.
Sevilla have got even worse in general this season. Because they aren't only bad in the La Liga now. They had a horrible Champions League period also. It was such a bad time period that they couldn't even qualify for the Europa League by finishing the group in 3rd place at least. They could have left Lens behind with their experience in fact.
That last game in the group between the two sides was critical for that but Sevilla just lost that one too.
I would have liked to see them in the Europa League honestly as something interesting happens to them there. But I must admit that they didn't deserve to be a part of that competition too this season.