Hopefully there'll be less placeholder mobs much over level 50 in the new world so it'll be easier to explore. There's really no reason for it until there's a level cap increase.

It's no big secret 1.0 was highly unfinished, so it was probably more work than it was worth to redo every area of the map when the new team came in. Once they started adding content to certain areas, that's when they made minor revisions to monster levels and such.