Armor makes you easier to heal, yes. There is no armory link so I can't check your values. For ICC, you want to be about 30k armor and up. Stacking stamina is NOT the problem.
EH is a combination of your armor and hp. The ballpark is 11 armor~1 stamina. Go for the gear that gives you the highest number adding them up that way.
Armor does not affect magic damage. Magic damage heavy fights favor pure stam.