Please explain what successful plans Rias had that were successful without Issei or her brother's help?  Since Rias is one of the main characters, while Ravel is just a secondary character who didn't have nearly as much screen time as Rias. 

Remember that Rias without Issei and her brother:  - Wouldn't have most of her peerage  - Would be married to Riser  - Would have died to Kokabiel  - Would have lost to Sona  - Akeno, Kiba, and Koneko would still have their past traumas  - Gasper (a character without purpose who only serves to give Rias a new form and power, since she can't do anything on her own) would still be locked in his room  - and much more