Which is a flaw, not something to emulate further.
Uhh… no, it does the opposite of that. It will probably spread people out into old zones more if you add something like that, which is great - except as soon as they’re done they disappear into nothing.
TESO uses the megaserver concept. You have one server and it creates however many instances it thinks it needs to make a populated world.
It does certainly do that, but it also creates a world where the fact that there are other players doesn’t really matter much because it’s constantly remixing everybody into new buckets. WoW has this problem, too, but mucks it up further by also having realms that aren’t fully merged, causing some sort of megaserver phasing without being a megaserver. It’s bizarre, and terrible.
If every player spends 1/3rd of their time then there are 1/3rd as many players in the game world at any given time. Of course it matters how frequently people are in there and how many are in there, but it’s not like them only being in there some of the time just solves this problem outright.
In fact, you’ve created a tension in the design - you don’t want players in there because then they’re not adventuring, but you do want players in there so they can enjoy all the stuff they got?
How about you get to enjoy the stuff you got while adventuring? Yes, that sounds good, doesn’t it? Que every other reward system in the game, no exceptions.