From what i saw on your armory, your hit and expertise are very nice. now they are not cap'd but with those numbers, there is nothing else u can improve upon until gear upgrades. Since threat is based on gear, all you are missing is replacing those few pieces here and there and your threat should jump to normal numbers. From experience, i was in full heroic drops with some naxx10/25 pieces, pushing 4k tps with 15 expertise and 180 HR. after a VERY lucky naxx 25, where i got a ton of new drops, my expertise is now 18, HR took a plummet down to 108... but my tps shot up to 7k+. thats my only answer i can come up with. anyone else can take a shot at it, but im sticking with what i got.
Heres my armory if u want to take a look: The World of Warcraft Armory