I meant the ip's you can traceroute, so the large nodes of the net.Or, you know, overflow isn't applying to login and the millions of people trying to login are potentially flooding it, as happens with almost every major release? Even if overflow is working on login, it's most likely not going to work for the database servers (you have a login server to process auth details and another server or cluster to handle databasing to prevent your databases being visible on the front-end). The sheer amount of traffic from "prerelease preview" is expectantly high and it's causing issues.
It depends entirely on the setup. They should have more than 4 servers, yes, but if you're referring to datacenters, then they could potentially have 50+ in each. You don't buy a single server in a datacenter. If you only need a single server, you go through a third party as it's cheaper (and often, you'd go into Cloud due to the potential savings you can make). You buy a cluster when you go with a datacenter.
If you're referring to routers (since the line before it refers to them), then less routers = lower ping. These aren't the routers you've seen sat under your desk or wherever. These are routers designed to handle massive throughput. The function similar, but their firmware and hardware is designed with much higher utilization in mind than a consumer router.