I've been sitting around the 2200 - 2400 rating (wow...just checked, I WAS at 2200 rating at about 1600 rank...now at 2150 rating at 4719 rank! What a huge drop!) Even here most aren't running a weak defense. What Yup said, about 1 in 30. It also seems like 80% of the people I hit with a weak defense aren't attacking back.