Mainz are not bad in defense. But they had better keep their scoring as high as possible. Their performance so far deserves a spot for it in my opinion. 
Mainz's attack is quite weak. Even then, this team is able to perform well consistently. This is definitely commendable. Although the attack is weak, since Mainz's defense is quite strong, we can see Mainz gaining points in most of the matches. Mainz has won four of the last 5 matches and drawn one. Mainz is in very good form.
Mainz is going to face Dortmund in the next match. Although Dortmund is one of the renowned teams in the Bundesliga, Dortmund's performance has been weak this season. The team is not even able to make it to the top 10 of the points table. Dortmund has even lost in the last two matches. Dortmund is most likely to lose points against Mainz. The match will be a draw, the new Mainz will win.