As far as best Defensive Guards right now, I'd go: (in no particular order, here)
Kobe, Iggy (when he plays SG), Rondo, DWade, CP3, Lowry, Kawhi Leonard, Thabo Sefolosha, Tony Allen...........Avery Bradley?
I even list DWade subjectively, because when I see him on Sportscenter, it's often for a chasedown block or something. I know he's one of the better defenders, though.
EDIT: I take back that last sentence about Wade. He's a legit defender. The man is averaging nearly 2 stls, 5 rebs and 1.3 blocks so far.