Traditional servers are essentially pointless at this point, why not have people be able to change servers on the fly with different servers for different game purposes (raiding “world”, pvp “world”, etc) and have a larger feeling game community. I think it would make the world feel more alive. Maybe the wow population is too high for that or the engine is too poor to handle it, but you could alternatively have a few very large servers where each server has different worlds to manually switch between.