We've never really even seen him use genjutsu though... The most we've (or at least me...) seen of it is when he used that really simple genjutsu on Danzo and some during his fight with Itachi (and again, it didn't come off to be really complex genjutsu).
Also didn't like Obito or someone state that Sasuke isn't all that great when it comes to genjutsu? I'm probably wrong on that, but something tells me I've heard something along those lines before.
And also, hasn't Sasuke only had EMS for a few weeks at most? Not really much to improve on with that. He really seems to be more of the taijutsu and mainly ninjutsu type anyway.