The servers get listed on the main id masterserver. dpmaster sits in the middle and fetches/filters the stuff you need so it's not the end of the world if dpmaster is down. It does an effective job. No point in taking on the responsibility to what the main q3 masters have been doing for years.
It will always get the data from the dpmaster for the ingame browser, even if you send heartbeats to other masters.
If there ever was a major issue and a new master server was required for some reason then it would mean astarting the game with an additional option to change the default master server to another domain.
There are lots of gaming site lists and you'll find your server ends up on most of them anyway. You could even just create a list of favorites... do something neat and have it autoupdate
Yes the memory issue is a pain in the arse.. I think it's malformed packets or possibly exploits causing that shit