Do the redskins have one of the best defenses in the NFL?

All the teams they have played so far are in the top 5 in offense so far this year, and the skins have basically shut them all down with the exception of Arizona. The saints only had one good drive against the skins all game, the giants only scored 16 and that was in the first half, the cowboys couldn't move the ball on us except for two drives they had, the cardinals were really the only team we had trouble getting off the field, but even then they only scored 17. So what do you think?