I can't help noticing your hit and expertise aren't capped.
Stamina ain't all that matters now for Tanks. No point having high hp if you're going to lose threat or be squishy right?
You gotta hit those caps. Those are the most important criteria for now.
With regards to gemming, i'd go with:
Meta - http://www.wowhead.com/item=52293
Red/Blue - http://www.wowhead.com/item=52221
Yellow/Blue - http://www.wowhead.com/item=52231 OR http://www.wowhead.com/item=52237
For your enchants, it seems pretty fine but personally i'd make some amends such as:
Bracers - http://www.wowhead.com/spell=62256
Weapon - http://www.wowhead.com/spell=74244 OR http://www.wowhead.com/spell=74195
Pants - http://www.wowhead.com/item=56551
Boots - http://www.wowhead.com/spell=74189
Remember to grab the belt buckle: http://www.wowhead.com/item=55054 After that, put in a http://www.wowhead.com/item=52242
Hit > Expertise > Parry/Dodge > Mastery
You should be reforging to dodge/parry over mastery if you have less than 4600 combined avoidance rating (mastery + parry + dodge).
Hit cap is at 8% & Expertise at 26.
For Flasks, i personally like using:
http://www.wowhead.com/item=58143 (Since most fights has magic now, it really comes in handy)
For Food buffs, i'd use:
http://www.wowhead.com/item=62664 (If you're having difficulties with threat or not expertise capped)
http://www.wowhead.com/item=62663 (Basically AWESOME)
Be sure to keep your shield block up whenever it's available, Demo Shout & Thunderclap too.
These skills help alot to minimise damage taken towards you.
With all of these, you should be more or less ready for raids.
For some fights, you may notice yourself taking lots of damage. It usually happens due to:
1. Someone doing something wrong in the raid.
2. Specific boss just more healing-strained for the raid.
I hope this comes helpful to you.