Without seeing the site in question it's really hard to weigh in meaningfully, though the bloated slow insecure train wreck known as turdpress could be a likely contributor to your problem, particularly if you are scripting heavy, extension and mod heavy, and using some fancy but ultimately useless off the shelf template. Most such things being little more than scams used to trick normal people into thinking they can have a website.
How many separate files is a typical page serving? How big is the file total? How many domains are you accessing? How big is the markup and the constructed DOM?
Without seeing the site and as such being able to answer those questions, it's really hard to say anything meaningful apart from wild guesses.
... and @burak -- throwing more code at it is not the answer. That's just sweeping deeper rooted issues under the rug -- such nonsense not being needed in 90%+ of cases if people would bother learning how to use HTML properly and didn't load up on hundreds of K of CSS and scripting for NOTHING of actual value to site visitors.