I've posed this question to support at various times with no answer, so I thought it time to survey the community.
Ever since we implemented our Aruba wireless last summer, I see the usage graph do things like the following from time to time:
It seems to be in the afternoon, which would correspond to our higher throuhgput times. My understanding is that the left graph (overall throughput) is the outside of the controller, while the right graph (throughput per WLAN) is the APs. In our case, the graphs should be identical. Has anyone else seen crazy drops like this?