So, I had to test this myself and here is result.
I can't use this configuration because of two reasons.
1. In nstream dual, you can't use wds. Wireless bridge is impossible.
router - RB532 - wireless - RB532 - router
I tried to avoid this by routing, but mikrotik has so shitty ospf implementation, that do not work in our enviroment (debian Linux quagga). It do not even find neighboor ospf router.
2. nstream dual works fine on the desk, but when splitter was used it overloads each radio by noise and interference, so only 6-18mbit modulation was used, and real throughput was about 1mbps. Splitter that I used has >30dB separation and it wasn't simply enough. I tried frequencies from 5.1Ghz band on RX and 5.8 on TX, etc.
Has anyone success with those dual feed horn antennas ? I have never seen those. Any url ?