I dislike "Advanced Stats" as they are easy to manipulate, and one can always find an example of why they are meaningless, but Bledsoe's defensive impact is obvious.
Without Bledsoe, the Suns were 18th in the defensive ratings, giving up 106+ points per game on 47% shooting. Since his return, they are allowing 44% shooting and around 100 PPG. As a team, they are only behind Chicago, Indiana, Memphis, San Antonio and the Clippers.
It's amazing what keeping your man in front of you will do to your team's defense. Not only does he keep his man in front of him, but he allows Dragic to slide over to guard the opposing SG/SF so he can stay in front of his man. I am a huge Dragic fan, but he just cannot guard quick point guards.
While I don't think Bledsoe makes anyone around him better on offense, he makes everyone around him look better on D.
I really don't think most people appreciate just how good Bledsoe is defensively.