It is basically one mediocre RPG with lots of DLCs. Some better, some worse. But it would make housing easier. One ward, 1 house or apartment. Yours.
It would be like multiplayer in old FPS games where you're alone until someone joins you, or a Minecraft server, or... an RPG with multiplayer option.

But that would require to rebuild the game from scratch and change some things, like dungeons, raids, ally raids, etc.