the reason why you would go for the earthguard chain as opposed to the dps neck is the defense rating. you aren't close to uncrittable almost 60 points away. your bastardizing the useful portion of gs by boiling it down to a score regardless of gear/role compatability. the addon is only useful if the gear that the score is based on is meant for the role. my feral druid can have a gs of 5000 in all resto gear but that doesnt mean anything. until you hit 540 def rating i'd gem for it in all slots.

your boots, pants and cape are really nice but have 0 defense you could replace them with blues from the wyrmrest accord and argent crusade faction vendors to get a little boost... except you have like no faction rep in wrath.

as for darkmoon cards. i dont know but if i were you id chain run toc5 man until the black knight drops:

The Black Heart
Binds when picked up
Unique
Trinket
+126 Stamina
Requires Level 80
Item Level 200
Equip: Each time a melee attack strikes you, you have a chance to gain 7056 armor for 10 sec.

i'm not at all familiar with pawn but it seems like you would do better without it. at least on the tank. tank stats are pretty easy. def till 540 > stam> str the other stats associated with tanking come naturally for the most part. there may be an arguement to getting some hit/expertise to knock misses and parrys off the table but in the content that i think you would be doing i dont know that you need to worry about that too much.

speaking of what i think maybe you should tell us what type of content are you looking to get involved with?

hope i could help