I love nginx. But most of these are mitigation for DoS only targeting the web server, not DDoS. They're explaining how to throttle a single IP. The whole point of DDoS is to distribute the attack to bypass mechanisms that throttle single IP's (plus to amplify).

Also the DDoS attacks that we've been hit with actually target our uplinks by saturating them with traffic, not our services. We have a 1 Gbps port and the last DDoS we were hit with was over 20 Gbps, which is a relatively small one. The mitigation we used was to have our hosting facility get their upstream provider to route the traffic through a layer 7 DDoS mitigation filter provided by an external company. It worked wonderfully.

These are cool features, but when your link is saturated it doesn't matter what a daemon listening on a port does.