Cross Realms

Chicago

So i know cross realms would not work due to every server being unique with their own nodes etc, but a problem/concern that i have is this:

Although it is amazing with a world size of 600 ish kms, with server sizes 8-10,000 and a safe bet of 20-30% of people hanging out in cities at all times, it would render most of the world empty, i know a lot of games have failed because of this where it almost becomes a single player game as you never run into anyone in the open world.

is there anything in place to assist with this issue?