No. DMZ never seems to work very well for me. Forwarding the specific port used by Doom DC (5029 I believe) that's stated in it's configuration menu should be enough for it to work properly.
maybe there is another port? or maybe he had the wrong port down. He said he got it to work with psp and DC so maybe DC to DC won't work? I dont have bba but I would be able to help test on pc. I can set dmz up too.
Indiket and I tested Doom DC today. On our first try we connected and played a match on the first level. A little choppy playing over seas but it was fun. It seems the initial connection is very touchy. We tried at least 4 more times to connect but failed. We found no concrete rhyme or reason as to why we failed to reconnect but we plan on doing more testing.