The first thing that jumped out at me, though unrelated to your threat generation, was that you are activating you metagem with a purple gem placed into a yellow socket. Regem your helm and place that purple gem in your leggings.
The second spec should increase your threat gen by a noticable amount. The 2 points in focus rage and 3 additional in sheild specialisation could be moved around but will not really impact much in my opinion.
Could you post your glyph choice since has a great impact on your threat gen. More so that gems and enchants
There are several other issues all unrelated to threat gen, they include weapon enchant. Blood Draining is usually the one of choice.
Replace your chest enchants with 275 health
Consider Tuskarr's Vitality on boots
Change your trinkets to stam or armour ones. Most easily available are the Black heart from 5man ToC normal and Glyph of Indomitability from Emblems of Triumph