People have been calling for mob grinding to be a viable way to level since 1.0 went down and they were building 2.0. It will never be in the overworld like this so this, entirely self contained content has been created FOR those kinds of players. I was against it way back then citing it would be a boring way to play but since eureka has released I have played more often and longer than I have after any new content has been added and I havent even touched roulettes/dungeons/raids since. I can't even say exactly what it is about it I like but this feels more like an MMO than anything else in the game outside the initial rush through content like the Raubhan Challange. Even then no one was interacting, just standing around him trying to get in an instance.