If the DDoS trafic is so big the logs will not show all the trafic generated by nodes.
Also Proxy servers can be used in DDoS which is extremely hard to mitigate DDoS in this case.
The first piece on the network will be a router if the trafic generated by the botnet is that big the router can't redirect the packets, and in this case not even blacklist would be useful.
Tycho you should consider changing you host service. with the fess that you pay for the service I think you can spend some money on the service.
Changing to http://www.prq.se/?intl=1 PRQ would be magnificent. The most resilient hosting that I know. (Responsible for hosting the pirate bay).