mwallen,
It is very hard for us to determine what is going on this forum especially across ArubaOS software versions. You also did not say if you have wired, wireless or both types of users connected to the RAP that are having the issue.
Are you certain that the VLAN on the controller has bcmc-optimization enabled? Are you certian that "drop broadcast and multicast" is enabled on all Virtual APs on the access point?
Traffic from the RAP to the infrastructure if fully tunneled will never match the performance of the WAN circuit due to (1) Serialization delays (2) Reduced performance due to ipsec encryption/decryption (3) the variability of the internet.
When this happens, you need to look at the access in the access point using "show ap debug system status ap-name <name of ap>" to get a picture of how the access point is performing from a hardware perspective.
We are not able to gather enough information about your infrastructure on this forum to determine what is going on conclusively, because your problem could be so many things. I would open up a support case in parallel, because we do not have enough information to replicate exactly what you are seeing.