I've got a lone R500 I'm trying to configure band-steering on but with the latest firmware there is no set/get band-balancing from CLI.
If I downgrade to 9.8, there is a set/get band-balancing from CLI, but no matter what I set the 2.4 or 5 radio RSSI to via set band-steering wlanX my iPhone 6 always prefers the 2.4 band. (same for other wifi clients)
I have a ticket on this, though I can't see it in my support portal for some reason.