I have just started tanking on my dk. Im in full T-7. Im def capped at 540. my question is what enchant i should get on my cloak. Im thinking either +22 agility or the +16 defense. Im just not sure which gives better returns. Thanks.
If you are having to use any 8 defense/12 stam gems in blue slots to reach the "cap," go with +16 Defense. It will allow you to swap 2 of those Enduring Forest Emeralds for pure 24 Stamina gems, thus the enchant effectively becomes +24 Stamina.
If you don't have to specially gem for defense to reach the "cap," I'd go with +22 Agility. It's a good all-around enchant that gives you some dodge, armor, and crit for threat.
225 Armor is not bad, but kind of outdated. Not much bang for buck by WotLK itemization standards., unless you are just going for pure Effective Health above all else.
+16 defense is for tanks who aren't uncrittable, or for a pure avoidance set (which you don't *need*, nor want, for any of the encounters).
Avoidance isn't bad. Breaking up back to back hit strings with a defense enchant can be more valuable than getting hit for a bit less damage with an armour enchant. Back to back hit strings are more likely to put a tank into danger than a slightly larger hit.