Feynoord win Vs Bayern was another shocker for me, in my wildest dream I never believed that Bayern could lose with such a wide margin against a team like Feynoord, this proves that no team should be underestimated. Although Bayern even hasn't really been themselves. After match day one which saw Bayern score 9 goals against GNK Dinamo, I thought Bayern will be on the same level as Liverpool currently is in the UCL but I was to have overestimated them this season.
What actually shocked me the most about the result of the UEFA Champions League game between Feyenoord and German giants Barcelona was that the Dutch club succeeded in stopping one of the most potent attacking line in Europe from scoring a single goal. I don't think there's anyone who must have predicted such result and that's why many are still surprised about the outcome.
Just like you suggested, Bayern Munich's performance this season have been short of the expectations of many and if nothing is done about it to improve their performance, they'll likely be eliminated from the competition and that I don't think is what fans of the club would want to experience