There is 15-25% packet loss to those users that are coming in on the Level3 Communications network. That's why pages are loading slowly for clients whose connections are coming through Level3 communications.

Level3 Communications is a carrier in proxy between the datacentre and your ISP's, meaning it is not an issue of the datacenter, and not your ISP's so there is little we can do about it right now except wait for Level3 to address the packet loss.