I agree that Leverkusen was always strong and they were even racing at the top of the table with Bayern Munich and Dortmund but they are much stronger this season with their coach Xabi Alonso. They had a good performance in the last season but Leverkusen didn't have many good players and the team tried to help Xabi by hiring the players he needed, that is why they are in the top side of the Bundesliga because Xabi Alonso was a great advantage for them.
Xabi Alonso success in managing Laverkusen this season has been phenomenal, going seven games unbeaten and topping the Bundesliga standings. I see Bayern Munchen dominance starting to be threatened even though they have better squad depth than Laverkusen, but in terms of strength I think they are quite balanced. The draw in their second meeting in the fourth week is proof of Laverkusen strength this season, just waiting to see how Laverkusen strength will be when facing Dortmund.
The Bundesliga standings have become more competitive with Laverkusen consistency in winning points, if this continues their chances of winning a trophy at the end of the season are wide open. Thus, Munchen decade-long dominance was broken by their own former midfielder Xabi Alonso. Dortmund almost did it last season, finishing on the same points but falling behind in the goal statistics.
So far in the Bundesliga, we know Bayern Munich has a much better squad than other teams like Dortmund or Leverkusen, and even Stuttgart, but still Bayern Munich couldn't get good results like these teams got so far in Bundesliga games.
Stuttgart's performance was amazing so far thanks to their palyer Serhou Guirassy and Leverkusen got a coach like Xabi Alonso who is a great advantage for this team.
Bundesliga Bayern Munich is a strong team and they are doing well but the problem is that the two teams you mentioned are performing better than their expectations which is why Bayern Munich are not going to the best position in the Bundesliga despite their consistent performances. Bayern Munich will need to continue their streak in the Bundesliga until the end of the season if they are to win the league title this season.
Leverkusen, Dortmund have been performing consistently but it is difficult to maintain their consistency till the end of the season.
No matter how the other teams in the league perform, Bayern Munich should focus on their performance so that they don't suffer and if they can stay consistent, everything will be in their favor.