What is your trash rotation?
A) Enchants, if it's 346 or higher and it's not enchanted, you're doing it wrong. Basic truth, you need raid drops to replace most of it so enchant your gear.
B) Stats Mastery > Parry > Dodge > Stam sub-hardmodes. Parry =/= Dodge because of Hold the Line. Parry is actually better than dodge, how much better depends on the amount of mastery (block + crit block) you have. The more you have, the better parry is compared to dodge so the deeper into DR parry is than dodge in order to maximize the effect of HtL with the increased DR of Parry.
Yellow/Prismatic/DPS Socket BOnus = 40 Mastery
Blue = 20 mastery/30 stam
Red = 20 mastery / 20 parry
C) If you're serious about tanking, all gear should be reforged. If it doesn't have mastery, reforge something into mastery and then usually parry (sometimes dodge). Reforge away from DPS stats first (crit/haste), then threat stats (hit first, then expertise), and finally, usually away from dodge before parry.
D) There's a lot to get your head wrapped around. The primer I wrote in my sig isn't perfect, but it should help you understand Cata tanking as a WarTank and then any specific questions or clarification you need, feel free to ask :-)