On Mac OS X 10.9, when connected to my 5ghz wifi, I can only add a wired printer via IP address. When I attempt to install it using the HP installer (or simply via the add printer dialogue) while connected to 5ghz network it is not discovered. However, on the 2.4ghz network it works fine.
Is this an AC access point? What FW? Is it standalone?
It sounds really similar to some issues I had when I first got my R700, where broadcast (Sonos) and multicast (Bonjour) packets were unreliable on 5GHz after some hours of uptime.
I worked around it by adding a controller, which made the problem magically go away, and I got too busy to hunt down the original issue. I read the 9.8.2 MR release notes had references to fixing a broadcast issue on AC AP's in standalone mode, so perhaps this is resolved in 9.8.2?