I really sympathize with you. Over here on version 5.1 our response time for damn near everything is just below 10 seconds. We're basically told one of two things: 1) Its just your imagination. Your users are spoiled brats. 2) 10 second response times is perfectly reasonable for your complexity and hardware and no, you can't have a performance guide to set your expectation by.
I hope you find a better solution than ours (re: "live with it"). You may be happy to know there are plenty of other tools out there with WAY better performance.