User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-2602:306:CD9A:C860:141A:858E:1B9B:BDB-20190201001403/@comment-28884330-20190201215507

I think the reason for Rias' defeat, other than being inferior in specs, was just lack of focus. Even with her lack of specs compared to Issei's team, she never seemed to attempt ganging up on Issei of all people. She had enough specs for that at least, as Issei couldn't have dealt with a tag team of Crom Cruach + Strada or Crom Cruach + Balor Rias, much less if the three of them managed to get him.

With his new power up, it is likely Yuuto could have dealt with most people in Issei's team short of Issei, Ddraig and Asia due to her particular strengths. With the support of the rest of Rias' team, they could have maybe cleared the way for the pwoerhouses to check Issei before he could summon Ddraig, and that would be checkmate.

However, she spent way too much time trying to clear them one by one and go for 1v1s, rather than have a more focused plan of action.