This is probably done to prevent 'zone crashes' that seem to accompany the spawn of King Behemoth and Odin. I can't remember the last time I tried either of these without DCing at some point trying to enter the zone.

Don't worry -- this should only be an 'issue' when these two monsters spawn, and at no other time. I suspect there was no way to 'limit' the people in each zone until now, thus resulting in the crashes. This will just make the zone more stable.

Now if only they would prioritize engaged mobs over players... we'd actually be able to see the monster, avoid abilities, AND get a gold medal for completion.