First off, there's really no reason to gem for defense, dodge or parry, not even for set bonuses. If you need a yellow gem for a set bonus, grab hit/stam. If you need a red gem, get expertise/stam. Looking at the stats, and keeping in mind that you'll have full Anticipation when in tanking spec, there's absolutely no reason to be gemming for dodge.
But while your hit is solid at 253 hit rating, your expertise is a low 14, only granting 3.5% dodge/parry reduction. That's not enough: you'd probably want at least to shoot for the 26 that pushes dodges off of the melee attack table at the minimum. Everywhere I see a dodge/stam gem here I'd prefer to see expertise/stam until he was at least at 26.
Your talent choices are solid: you go for Improved Demoralizing Shout, very useful against physical damage bosses, instead of Impale/Deep Wounds for bleed threat. It gives up some AOE threat but it's definitely not that unusual. Your five points in Deflection make the parry gemming even less relevant.
Your hit rating is high enough that you can probably afford to drop the Glyph of Taunt as you are most likely not getting all that many resisted taunts purely on hit rating. (Technically Taunt is a spell, so the hit you'd need would be higher than the melee hit chance, but once you're close to 300 hit rating the glyph really isn't that necessary.)
And with a block value as low as this gear has (the only places you have Block Value are on your shield and hat) the Glyph of Blocking simply isn't all that compelling. 10% more Block Value after a Shield Slam is what, another 140 block value? The Glyph of Vigilance will easily provide more threat than that. Likewise, the Glyph of Cleaving will allow your cleaves to hit an additional target for more tanking AOE threat (which this spec doesn't produce as much of due to the lack of Deep Wounds/Impale) and the Glyph of Shield Wall will basically allow you to have a cooldown available every minute, which is very useful when tanking hard modes and high damage bosses. I would definitely consider replacing those two glyphs, maybe even carry around a stack of Vigilance, Cleaving and Shield Wall to slot in depending on the fight.
To sum up...
In general, gear itself is solid, gems could use some tweaking away from stats you already will have in abundance towards threat stats you're low on (especially expertise, which at 14 really needs to come up), talent choices are solid for the Imp Demo debuff (but if you have an arms or fury warrior in the raid, get THEM to spec for the Imp Demo/Commanding Presence buffs and get yourself the crit from Cruelty and the threat from Impale/Deep Wounds) and I'd consider adjusting my glyphs around. By themselves all minor changes but I think you'd see a nice cumulative effect.
Check out more strategies, tips and leveling guides for Warriors in Matthew Rossi's weekly class column: The Care and Feeding of Warriors.