Oh Lord Mark, Good luck. We're all Mac and have been struggling mightily with this issue for years. I'll step through what I have but I've not found best practices. This really seems to be a moving target for Apple with Wi-Fi updates coming with nearly every update.
- Can they upgrade the controller? Extreme has made several changes that specifically deal with Apple's "improvements." I'm on 09.15.03.0005 with the APs purposely on 09.15.02.0009.
- End users really need to be trained to turn their Wi-Fi off and back on again. This solves connectivity issues - most of the time.
- Macs have a problem with caching bad info and good luck finding it. There is nothing that I know of that's akin to doing a "repair" on a windows machine which seems to always fix the issue. Here are the steps which must be done in order though:
- Turn off Wi-Fi
- Remove relevant keychain entries
- Remove relevant Wi-Fi networks
- Remove any 802.1x profiles
- Delete the AirPort's location
- Create a new location
- Turn the AirPort back on and try again.
I know the above is tedious but I can't stress enough how many machines it has made better. If you find this to be helpful, let me know - I have a script which can be adapted to your location.
- Macs seem to have a way harder time finding the best signal than Windows so they'll latch on to a poor signal and all-the-sudden go looking for a better one. I've had SOME success shrinking the cell size, but Extreme told me that what I shrunk it to is now the default: MBR for the A/N radio: 12 Mbps. I've had (and kept) the MBR for the G/N radio at 6 Mbps (which is the default for that radio) due to low density issues in certain areas.
- Revisiting problem areas to re-channel if necessary.
- If any Apple client is not up to date, have them turn off Bluetooth(or update!). This problem seems to be solved with 10.10.2 (not sure about iOS yet).
- References:
- A lot of banging my head and the bricks.
- My testing shows this to be fixed in 10.10.2: https://medium.com/@mariociabarra/wifried-ios-8-wifi-performance-issues-3029a164ce94
- No clue what to do about this one except the wifi off/on trick: http://www.reddit.com/r/apple/comments/2zo1uo/if_you_have_still_having_wifi_issues_with/
Hope some of this helps - at least know that you are not alone.