No no no, I'm not talking about those elite spawn with the skull and bones icon, I'm talking about actual World Boss! A gigantic boss with actual mechanics, spawn every 1 or 2 hours, requires a full *** of people to take down (just like a domain, but have actual challenge), and drops 2 or 3 set items a time.
Also, have you ever played Skyrim? Or maybe Imperial City sewer? Have you ever had the feeling of caution while knowing there's a super powerful boss roaming the ground, who can appear any moment and send you back to the local wayshrine? Well, let me tell ya, it's a hell of a thrill drive. Here's my suggestion, why not introduce to people who has never experienced it, with a new kind of boss: Roaming boss (such as Dragon in Skyrim). These boss will be super tough and random (but still possible to be defeated solo, but super hard), each zone with 10 to 20 of these guys, and drop named set items associated with that zone, so people will know that you've defeated such a beast?
I don't wanna criticize ZOS on their world building, since they've been doing a very good job, but I believe the lands of Tamriel need more... flavor. Also, we players (especially new comers) really need some kind of fun activities we can do with our small group of friends.