They need to have a you're-actually-on-your-home-server new world bonus. Something other than Road to 80 (which "follows" you between DCs), or just making Rt80 only apply when you're home.

What's the point of a new world incentive when it doesn't have any sort of captive element? The one thing that might draw midcore/progressing players (because what do RPers or endgame players making alts care about having an EXP buff? Okay fine it helps them blitz through the game faster so they can buy a home in whatever expansion housing zone they want) doesn't actually require the midcore players to stay on their home server, so you have either a bunch of early-game and/or trial players in ARR and HW content who probably don't even realize you can DC travel, or (speculating cuz I'M only just at the end of SB myself lol) maybe people at the endgame areas?

And otherwise, the 4.x and 5.x content is ghost towns because anyone who's progressed that far in the game probably also knows how to DC travel, and does so because there's no reason not to.p