Now that there is a Mac client, your engineers will have access to the "Instruments" tool. This tool is practically the stuff of science fiction -it is that good. I strongly suggest taking a look at its capabilities, and using it to profile some of the known laggy cases, like logging in to the crafting hall, and see where the time is going. Double-click on the methods taking the most time and it will take you straight to the color coded source code with embedded percentage read outs.
One of your top competitors uses this tool extensively to find out where lag is occurring. It is extremely powerful and easy to use.