What are you even basing this on? They've won 5 out of 6 games in the group stage and had 1 draw. They've won 3-1 aggregate against Lazio and are now in the quarter-finals.
You're probably thinking this just because of the fact they're losing the league to Bayer Leverkusen currently being 10 points behind. That's true, but it's not about Bayern being weaker than in last season, but it's due to Leverkusen playing exceptionally well.
The average points/game in league games for Bayern is 2.31, in the last season, it was 2.09. If they keep their performance consistent, we should expect them to finish the season with 78 points, while the year ago, they won the league with 71 points.
I think they're doing pretty good.