Man it would be terrible if the NS2 server got DDos'd so the one that people actually care about and are here for actually fucking works.
Also I want to point out that I was on wcs for a few hours during very bad ns2 lag and never saw any issue on the server. The only times when the servers will be effected from eath others performance is due to disk bottlenecks on map changes and if the system runs out of ram due to a memory leak.
The reason why the ns2 or any other server does not directly have any impact on the performance of the other servers is because there is eight cpus for them to run on. As a result the NS2 servers have their own two cpus and the css servers run across the other 6.
The only time I had any lag or reg issue was when I went back in time to die and sure enough the guy that killed me had over 200ms latency and so this was not anything on the server side but purely a result of imperfections in online gaming.