It's taking approx 1944 miliseconds for a size of 250 documents, if I remove the highlighter from the query I'm getting 977, that's 967 extra milliseconds for the highlighter which tells me something is causing it to run slow. I'm using the FVH highlighter, here is the output from the hot threads which also seems to indicate it's the highlighter.
With the CPU usage being high could it simply mean that we need more CPU power?
They are quite large, we index content from PDFs in a lot of cases more than 1MB. It's not absolutely necessary. By default we offer the user 10 results per page but they do have the option of selecting a maximum of 250.