Welcome to Early Expansion tanking.
like you've noticed The stat scaling is extremely low at the moment, so since people are used to 20-25% dodge and parry with 20%ish block from Wrath, people are definately going to notice a big difference in overall damage taken since we're hovering at 10-15% block and parry.
Towards end of expansion raid gear, blizz basically throws out secondary stats like candy, and we basically gem for stats like stamina, but for early expansion it isn't bad if you decided to gem a bit into dodge or mastery. Which brings me to my next point,
MASTERY IS YOUR FRIEND D:
when you block, it mitigates 30% of that hit that would have otherwise hit you for 100%. As of right now, you can do alot more by raising your mastery instead of say parry considering that you can get your mastery up alot more than parry or dodge (it'll make your overall damage taken lower). Dodge is the same as parry but for dodge you can dodge attacks from behind so it might be a little better.
I'm guessing you're reading a item spreadsheet seeing from what I see from your gear, Threat isn't going to be a very big issue in dungeons and shouldn't be if mark your targets with skull and what not.
You might also want to change your spec around a bit.
You definately want to spec into Judgements of the Just because that's alot of damage reduction by itself, and unless you're using consecrate and hammer of justice A LOT, it's not really necessary to spec into hallowed ground and improved HOJ, you have your hammer of the righteous that hits like a truck. Reckoning is good for Single target threat, but we're not at the point of the expansion where we're lacking in threat compared to the dps. Also with the new vengence mechanic, Threat shouldn't be too hard to handle atleast for heroics. even without Reckoning, this is a bit of a personal preference but unless you have speed enchant on your boots you might want to get Pursuit of Justice, because you can get to the mobs a little bit faster incase you do want to get the interrupt off on that far away more or what not.
other than that, it's just all about interrupting casts, and popping your cds at the right time at what not. During wrath I didn't pop my tanking CDs at all for heroics but nowadays for some pulls you have to pop them to survive.
There are some pulls that are almost impossible to tank and someone needs to kite one of the ads because they're not cc-able. Obviously people will be able to overgear past this but for now, have someone kite those ads or offtank for them.
Edited by Biioe on 12/28/2010 12:13 AM PST