User blog comment:B214/Talk About What You Want! 3/@comment-72.240.208.36-20150415054601/@comment-26209278-20150415105608

Remember Rias nor Raynare knew Issei has the boosted gear. They dont know what sacred gear he has. Raynare was just told he had a "powerful sacred gear". Rias would of most likely given him up, she had no affiliation for him and was not aware of his potential power until she used all 8 of her pawns to revive him. She didn't know what it was that caused him to need 8 pawns, just that she needed all 8 when she tried, and that there was "something special" about him. (May be going off from the anime in that last sentence)