The fix is live on the US:
http://www.wowhead.com/news=280875/n...fixed#p4149582
Both old raid bosses and MoP lvl 90 / WoD lvl 91-100 mobs are scaled more or less back.
Non-raid mobs prior to lvl 90 are still bulkier than before, but at least the biggest problems (well, what I think were the biggest problems) are solved now.
Good!