I see nothing particularly wrong with your gear, although you do seem to have skipped a few hellfire/zangar quests that would have upgraded your rings and neck pieces.
The Cleansing Must Be Stopped - Quest - World of Warcraft
for example.
The quest reward rings from hellfire have mp5, which is not the most useful shadow priest stat in the world but it'll hold you till terokkar's better ring rewards.
You can also cherry-pick quests for item rewards if you're in a hurry to get to northrend and just want something better than random greens:
Hellfire Peninsula - Quests - World of Warcraft
just change the zone and resort by item rewards to find your cloth pieces of choice. I reckon you'll want new shoes at the minimum, once you've gotten better rings and a new neckpiece.