Open world NM's adds a sense of realism to the world. Everytime you see a group of adventurer's running to Vrtra you go "OHSNAP! THE LEGENDARY ____ ARE GOING TO TRY TO BEAT VRTRA!"


It becomes significantly LESS enchanting when everyone and their mother is fighting vrtra at the same time, in their own dungeon. Both content is cool, But having truly only ONE of a mob in the world at a time makes it that much more exciting.