Having noticed frequent latency spikes, on a 60ms connection, I am wondering if there are other factors affecting latency.
For example, we occasionally have to sync with notifications from the friends list (status updates, online user statuses, and more). Even if these could be push and not pull architecture notifications, I am not sure if they could affect the in-game latency. Therefore, in such a case, maybe it could help if the social panel contents (and all of its notifications) could optionally load on demand (for example load / refresh the friends list and the notifications only when you have actively opened the social panel). Not sure if the same server architecture is used for the chat functionality too, in which case it would mean global chat disabling, unless enabled on demand; therefore, 2 separate architectures one for in-game party chatting and one for everything else could help.