You forget that Naruto and Sasuke were never always that powerful. If Darui wants, he could go back in time to kill off Naruto and Sasuke when they were at there weakest.lol
No one can really keep up with Sasuke and Naruto (specially Sasuke). In fact, there isn't anyone who could possibly even get close to their level, except for Lee, if he uses the gates, of course.