AFAIK D4 does that in some capacity. There are zones that scale from 50-100 for example and if you are below 50 you'll have a bad time. It's correct that once you visit a former zone the monster scale with your level but as soon as you have the mount you don't have to put up with them. And because of the game design (a lot of dungeons, world bosses, legion events etc.) it's a welcome thing that they happen all over the zones and are not restricted to some high level area.