well, gear doesn't have to get spell dmg to be good you know.
in fact, I found that scarifying about 30 spell dmg over some expertise and hit rating gives me more threat on single targets.
Think about it, 1% more hit on the boss with seal of righteousness is a big difference in threat, since holy shield and consecrations are not based on your spell dmg, but a % of your spell dmg.
I'm trying to keep around 400 spell dmg, and 2 % hit rating and 5% expertise.
My guild is at 4/6 in SSC, 2/4 in TK, and nearly 2 in MH, about the same as you, but we began BT this week.
Look at my armory if you want to compare, I'm full pve, but a single pvp gear.
http://eu.wowarmory.com/character-sheet.xml?r=Burning%20Steppes&n=Ragingsoul
looking at your gear, you have the T5 gloves that I still don't have, about the same avoidance (48%), and about the same defense, but I have 1k more hp that you.
ok, you have more spell dmg, but no hit and almost no expertise, so on single targets, bosses or trash, you will do about the same aggro than me, even less maybe when we have a sheep in our feets, and can't use consecration.