User blog comment:B214/Shin DxD 1 discussion/@comment-30230931-20180804194539/@comment-28884330-20180806234221

You are not getting a very vital part. How would the capacity to trick Issei affect him in any way when Rias' team does not have any way of trapping him?

Even if Rias uses his perversion as his weak point, how would she exploit it after the fact? How would she trap him? What would she even do once Issei is distracted due to his perversion? If she doesn't have anything to gain an advantage afterward, then Issei being distracted due to his perversion would just slightly delay Rias' team losing.