I have a guild mate who is facing someone with three times as many G12 characters, and twice as many zetas. I've looked at his roster and it's very trim. He has very few characters geared/starred/leveled that aren't needed for a legendary character. And he has most of those legendary charachters, including (but not limited to) JKR, CLS, and Chewy. While I can't see his opponents roster, I have no reason to doubt my guild mate.
I agree that GP isn't the best test. And I agree that it's going to be hard for CG to create a perfect system. But I feel bad for my guild mate because I don't think he stands much of a chance. I think he has a mismatch, and I think the current system is certainly capable of mismatching.