Use
Varnish, an HTTP accelerator. I use it on my Drupal sites. Haters can try DDoS all day and it doesn't matter. The webpages are cached and served from RAM, not disk. I forget the insane pages per second it can serve, but it's top notch. For example, Lullabot, a Drupal shop that runs the Grammy.com website for the night of the Grammys, use Varnish on it. It can handle insane traffic.
Thanks for the comments. Solutions so far describe how the pool survives without going down. The solutions offered describe that if the speed of the servers is higher than any load generated from the internet the server will stay in operation. So one target of the DDoS is not achieved, Server remains operable. Nice for the pool.
My problem with the DDoS is that they seemingly generate enough traffic so that my hashes do not get to the pool server properly. This target of the DDoS, or better Traffic Jamming, i. e. no communication with the server - is partially reached. Bad for me.
So I was looking for a solution of getting rid of the traffic jammers without having to go to a private pool. It is possible for the infrastructure providers to significantly throttle and black-list traffic offenders.