Your gear is sufficient for Uld 10 and 25, however to help with your threat issue I would make a few changes.
Drop Improved Spellreflection, its just not useful at all.
Remove 1 point from Cruelty
As nice as Iron will looks you just dont really need it.
And Remove 3 points out of Shield Spec
This will allow us 9 points to work with.
Put these 9 points into
Improved Heroic Strike (3points) - Allows you to HS with every attack
Incite(3Points) - Must have, this enhances the crit of your priority AoE threat skills
Deep Wounds (3Points) - When you crit your Tclaps/Cleaves you will apply a ticking dot, which again helps with your AoE threat.
When your tanking in Uld the most your going to be tanking at any one time is 2-3 mobs on a trash pull. Your partner should be holding the other 2-3 it makes it alot easier to progress through. Doing this allows you to drop the Glyph of Cleaving, replace it with Glyph of Vigilance, also make sure your throwing vigilance on the highest threat in your raid (usually a retarded warlock who would rather rip aggro while doing retarded dps rather than scale back to avoid a wipe). You dont really need to worry about sundering up trash a whole ton because it dies so fast, so you can easily afford to lose the Glyph of Sunder Armor, replace it with Glyph of Devastate. By using Glyph of Devastate you will apply 2 sunders to the target thereby doubling the threat generated by Devastate, and maximizing your melee raid dps because you now have your target fully sundered in 3 swings, 2 swings if you have another warrior in the raid that assists with the stacking of sunders.
Now dont get flustered over losing threat in AoE pulls. Marking the targets in advance helps direct your mindless dps on which to kill first. Even then you might still lose aggro on a target, which can and will happen. Warriors are the kings of single target tanking.
As for your Trinkets, I would swap out Defenders Code, for the Rune of Repulsion. In 3.2 Parry will be equal to dodge point for point, and parrying more will enhance your Blade Ward enchant, again allowing you to generate more AoE threat from the npc's attacking you. As for Repelling Charge, you wont need it, your already def capped and your Monarch provides more benefit then that trinket provides.
These are my suggestions on where to work.