User blog comment:B214/Shin DxD 1 discussion/@comment-30230931-20180804194539/@comment-33939194-20180806233457

You're not getting it. This goes back to what Sairaorg did in volume 10 when he used Coriana. Issei's perverted nature has been exploited as a weakness multiple times and Rias is aware of this which is the point. Dulio trapping Issei was mainly successfully because Issei was too absorbed seeing Gabriel in a swimsuit despite Ravel's warnings. Volume 5 has shown how Saji was able to trick Issei. The point is despite how strong Issei is, he has always been prone to falling into traps by those who are cunning. Yes, Baraqiel using castling was effective because the game was Object Break but it doesn't change the fact Baraqiel outsmarted him by using Akeno.

There are multiple ways Rias could outsmart Issei or lure him into traps because she knows him too well. There are times were Ravel won't be able to save him otherwise Issei wouldn't have fallen into Baraqiel's and Dulio's traps. Ravel can only do so much but not everything.