From Warherald:
"Game Update 1.0.6 introduced several changes to City Dungeon Itemization. These changes were intended to be part of patch 1.1 but were released prematurely with 1.0.6. They are part of our greater plan to increase the availability of rarer items in the dungeons as a whole. While the number of Sentinel Armor Set pieces dropped from bosses will remain reduced players can look forward to even more rewards with the arrival of 1.1!"