Here is million bucks question. Situation:
Tower A (RB493AH) supplies tower B and C with 22dBi flat panel 5Ghz antenna @ 5180Mhz.
Tower B runs R433AH with 2.4Ghz AP b/g (2427Mhz), 5Ghz AP (5300Mhz), Station WDS -> Tower A.
Tower C runs RB532A with AP 2.4Ghz b/g (2457Mhz) and Station -> Tower A.

When on tower B traffic on 5Ghz AP becomes >7Mbps, tower C and B CCQ goes down rapidly to 10-15% and p-throughput ~100-200kbps. When tower B 5Ghz AP is disabled - CCQ on tower C and B becomes back to 88-100% and p-throughput ~30000Kbps.

Towers B and C are stations to Tower A. With same configuration and hardware you will get your max if you turn on nstreme or NV2 protocol. You will get improvement, maybe this solves your problem. The best solution is to put another 5Ghz card in 493A (Tower A) and one more antena directed to tower B or C. So that you have two point to point links between Tower A-----Tower B and Tower A-----Tower C, and of course you must try any frequency combination because of interference between towers



Don't forget to give Karma