The addons code only reacts on events the server fires, so if the events take their time the addons will take their time as well.
-> Simply check it by disabling addons and do it manually and you'll know if it's an addon related issue
I think this happens due to server capacities and many returnin players. Especially if you list/interact with banks in a very crowded area.
Use any region where nearly any player is near you or in your instance. If it also is that slow it might be a server handled protection to slow everything down and make the servers more stable (ZOs needs to validate this, it's only a guess).