I just finished up the drop rates on all the gear that I can, with that being said because of the expansion being so new there hasnt been a whole lot of Heroic mode boss' downed. Therefore ALOT of the heroic mode raid gear is still going to show (??) until guilds start downing these boss'. Also the heroic mode gear that does display a drop rate may be skewed because of the same reason some items still have ??
Just have to be patient for these pieces of gear.