Core runs are still the fastest legendaries/hour right now, so it seems likely that they'll have to nerf chests next. (Either that or tie chest rewards to monster kills somehow).
I don't know why they haven't just cut down the number of chests that spawn there yet.
edit: already pointed out, should read more.
But making the rest of the game better is ... well, better. I mean, wouldn't the next step be to find the next best area for just popping chests? It's a band-aid fix to just alter Core.
It would be, yes, but Core's a really obvious outlier. There's no reason for a guaranteed corridor to also have the highest chest density in the game.