The newly-released official 5.2 PTR patch notes reveal that all T14 Normal and Heroic content is getting a 10% nerf. Guess that explains the Feats of Strength.
"On Normal and Heroic mode, zone-wide auras have been activated in Mogu’shan Vaults, Heart of Fear, and Terrace of Endless Spring, reducing the health and damage of all enemies therein by 10%. A NPC near the entrance within each zone explains this, and offers to deactivate the buff for the benefit of brave/foolhardy adventurers."
(Source: http://us.battle.net/wow/en/blog/822...y_30-1_30_2013)