I am having a slow and variable response time issue with my

I am having a slow and variable response time issue with my client's website, using the legenda theme from 8themes. Our big concern is slow home page load. Once the site is loaded,navigation speed is ok.

In conjunction with my hosting provider, we have tested/ruled out cpu usage, memory usage, and database issues.

Using tools.pingdom.com, I can see 80-100 requests made during the home page load.
Some page loads take place in 2.5 sec, while others take 60+ sec.

I have QuickCache on the server and I can see from its signature that it is working. I have gzip enabled via .htaccess. I have browser-side cache enabled. That helps, of course, but not on the first load. I've attached some results of testing. The difference between SlowRun and A Quick Page Load, which were two runs separated by about a minute, is surprising.

Is this an apache tuning issue?