User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-92.21.29.42-20190623153730/@comment-34061653-20190627181316

Indra's advice was irrelevant because he was pointing out that Issei relied too much on Ravel but here he didn't need Ravel to beat Rias in their fight as Issei already knows how to beat opponents using tactics because he's done it on multiple occassions. Issei only needed hia grandfather againat Thanatos but against Rias, he could the technique on his own without his grandfather's assistance. In short, Issei didn't need from an outside party.

Considering Rias has the most knowledge of him, the fact that this wqs the beat she could think of makes it half-baked becauase none of her countermeasures help her to actually beat Issei. Again, just a means of survivability. This is just like back when she faced against Riser. Despite knowing of Riser's regeneration, she didn't come uo with any countermeasures which ia ironic seeing as his regeneration is the reason she lost.