I cant see your gear cause the armory is down. If you are just getting the epic achievement than your gear probably has a ways to go. Get the level 245 helm. It has a nice amount of expertise on it. Now that 3.3 has hit just run heroics for badges and upgrade your gear. Being expertise capped is more important than hit for tanks. For multiple mobs consider using glyphs of cleave and sunder armor. I can't see your spec either but a typical 15/3/53 works well. On a side note, stacking stamina isn't everything. Your armor and avoidance stats are important too. Most new tanks have no choice but to gem defense in order to reach the 540 cap. With better gear gemming defense becomes unecessary and those gems can be replaced with stam and stam/exp gems. Having 32k unbuffed HP and being exp capped is fairly easy to reach with better gear.