Old post but I'm having the same problems with 912's. I've been jackin with these things for months trying to figure out what I'm doing wrong only find this post where apparently everyone is dealing with it.
My CCQ's are all over the place unless I limit them to MCS11 or 12. Throughput sucks. I've got one link that gives me real world traffic of 13 megs down by 85 megs up. Even though ccq says 100%, no cat5 errors. Replaced cat5 cables, feedhorn cables, 911gs with new 911gs. No help. If I reroute traffic through my backup link which is 3 pairs of RB711's, 2 pairs of Motorola PTP 600s, 4 routers, and 4 switches I get 4 times the download speed. LAME!
I love mikrotik routers, I really do. But you guys are gonna have to ditch the wireless game. Heads up, we're buying more and more ubiquiti over here. Only problem I've had with them in 2 years was a lightning strike.
Before mikrotik tells me to submit a trouble ticket I have 6 links using 911gs with similiar problems. And yes, I'm using the latest firmware.