I saw an NPC Carbuncle running around without a master. It would walk around aimlessly and sometimes a dialogue box would come up "<sniff> <sniff>". Been playing for about a year and never noticed this.
The Domans and Crystal Braves aren't there unless you've gotten up to them in the story but the buildings are the same for everyone. I haven't checked to see what is/isn't visible of the expansion content or anything though.
After playing FFXI for 10 years, I found it incredible they can turn on certain event tags behind the scenes so each player sees a slightly different town and can interact and even SEE different NPCs that other players can't. So if I talk to a Crystal Brave in Mor Dhona and there's a brand new player next to me, to him, it looks like my character's head is facing a blank wall? Whereas on my screen there's a blue-clad Hyur in front of it?