In my opinion Bayern is not performing averagely just that they are performing not up to their usual standard and the fact that Leverkusen is beating them to the league makes people think they are performing avaragely, although they are quite inconsistent with their performance but I doubt if they will take the inconsistency to the champions league.
Bayern Munich had some bad matches that cost them a first position loss to Leverkusen but about quality, they have good quality and if Bayern Munich meet Leverkusen directly, they can beat Leverkusen when they are ready for a direct match.
In a league competition that lasts through a long season, Bayern Munich fail to maintain their stability so that Leverkusen do it better and take the first position. In Champions League, where Bayern Munich must focus on now, they have enough power to win it. Many players in Bayern Munich already won Champions League but it's hard to believe that they no longer have motivation to fight for winning it again.