I don't think winning the Bundesliga title without ever losing can be called lucky. It was Leverkusen's hard work last season and they deserved it. This season Xabi Alonso's troops are indeed struggling, their performance decline is clearly visible and what is wrong with Leverkusen now is in their fragile defense, we can see from 12 matches they have conceded 19 goals. You can't compete competitively if the defense you create is easy for your opponent to pass.
Agree with you. Leverkusen's success last season was not a matter of luck but it was because of their hard work to continue to maintain their performance and at that time the spirit of all Leverkusen players was burning, including the coach. So winning the league without losing was not a matter of luck, it was the result of hard work so that they could be consistent until the end of the season. If Leverkusen this season is a little down, it is natural, because it is very difficult for a team to maintain the same success as last season besides this season Bayern Munich has indeed performed very impressively under Kompany's guidance.
And regarding the Bayern Munich match, we will agree that 3 points should be easy for Kompany's troops to get. On paper Heidenheim is not a tough opponent but that doesn't mean they came to lose, unexpected things can also happen.
Of course this match will belong to Bayern Munich, Bayern Munich will win easily in the match against Heidenheim, especially playing in front of their own supporters. Kompany's mission this season is to appear consistently in the league so that the points difference is wider than his competitors and then he can focus on the UCL league.