We have updated WoW Classic to make the NPC Archmage Angela Dosantos available at Light’s Hope Chapel.
Now, if you wish to complete your attunement to Naxxramas in advance of the raid going live on December 3, you can visit the Archmage and take care of it.
It’s not really gonna be the attunement NPC that’ll be locked down though. It’ll be the actual entrance into Naxx, which is close to strat UD (it’s a building a little to the left).
Unless they bring in what they had on the PTR servers, which was an NPC in each city that could teleport you directly into the instance. (It wasn’t there the first week of testing Naxx, but they brought it in for the later wings because of the massive lag in EPL.)