Resurrecting an old thread. We found that a default setting in the AP's may not be optimal for some clients - so if you are seeing poor band-balancing results try (on the AP)
set rpmkey wifi0/wlan-withholding-limit 7
This ups the number of probe/auths to 7
Preliminary testing shows this improves the band-balancing behavior for some stubbornly 2.4ghz clients without adversely affecting others. But you should test on your own client sets and be prepared to set it back to default (1) if you see adverse effects.
