Hi,
Yes, I have browsed the "Very High-density 802.11ac networks" VRD and high density APs should support much more than 64 users per radio. The following is an excerpt from that document:
Maximum Associations per Radio
For many years Aruba has recommended using a figure of 150 associations per radio for HD planning. This recommendation has been revalidated for 802.11ac and VHD networks. You should use this value unless special circumstances apply to your deployment.
VHD coverage should always be provided by dual-radio APs. Therefore, this coverage equates to 150 + 150 = 300 associations per AP. However, because 5-GHz is generally expected to have many more users than 2.4-GHz, you want to do your math on a per-radio basis.
When you plan the AP count, do not use the full Aruba capability of 255 associated devices per radio. You must leave extra headroom for the inrush and outrush of devices and poor device roaming behavior.