I have an 08 and mine still gets buzzy at around 4K RPMS. I still haven't found the reason. I gave up looking. I may try the handlebar ends. About the only thing I haven't tried.
There was a screw missing from the bottom of the mirror housing on my '08. At 3000 RPM or so it would start buzzing. Got a replacement at the hardware store, now I've got a quieter buzz I can't seem to find, I hear it in the same RPM range. It seems to be an ongoing battle.
Yeah I would definitely check the bar ends. It made absolutely no sense as the screws were tight and they didn't feel loose at all. I've put about 30 miles on the bike since fixing it last night and it's so much more enjoyable now.