I was asking this question few months ago. I was desperately needed a good wifi driver with my own kernel build. When I was dealing with this problem, the mac80211 wasn't just slow, it was also dropping connections and crashing the OS.
I've spent a LOT of time dealing with this issue, and in the end I managed to take LinkIt Smart OpenWRT image, configure it to my needs and deploy it on Omega2. It was a real hassle, because there are some hw differences and they're using an old kernel version (3.xx) with pre-compiled Ralink wifi binaries.