I haven't looked through this whole thread, so I might be posting stuff that has already been discussed but here it goes anyway just in case it helps some future googler.
I am a network engineer on staff with a small private university. I experienced problems with my wireless network around the time iOS 6 hit and traced the problem back to iOS devices. The problem came from devices violating part of the TKIP protocol called the Message Integrity Check (MIC). The issue came to my attention when our wireless LAN controller started shutting down parts of the network as a security countermeasure.
I am not sure what the end-users of the offending devices were experiencing but, due to the security countermeasure of my WLAN controller, the entire wireless network was bouncing on and offline.
Our solution was to stop using WPA and start using WPA2 with AES encryption.