For tanking slow, hard hitting raid bosses you want to stack effective health (armor and stamina).
You have a lot to work on. Your spec has no points in Improved Judgements, which tells me that you don't use the 96969 rotation - 96969 is the cornerstone of pally tanking and you should definitely learn it.
Do not worry about avoidance, other than gauging plate gear upgrades. Any tank gear you're wearing is going to have avoidance on it and it will be sufficient. As said, focus on stam and armor beyond that. And do fix your spec/rotation.
You have 5 abilities that you use in your standard rotation. Two of them are "6" abilities, three are "9" abilities (once you spend a point in improved judgements), based on the length of their cooldowns. In order to attain your maximum possible single target threat per second, you will build your rotation around using these abilities in the order 6-9-6-9-6-9 etc. If you are doing it correctly, after using every ability once, there will only ever be one of them off cooldown at any given time.
6 sec CDs:
9 sec CDs:
There is more to it when tanking multiple mobs if you want to min/max, but the rotation I've described will work very well anyway. Hope that helps.
A few simple changes i would suggest :
replace glyph of shield of the righteous with glyph of seal of vengeance - will help u get ur ekspertise sorted
get glyph of sense undead - why not use that slot since its there anyways
Loose benediction, divinity, and one of the points in spiritual attunement. You will never be short of mana as a tank in ICC, so you dont need benediction, and the 5 % healing from divinity usually goes into overhealing anyways. if you find yourself short of mana in heroics, simply switch to seal of wisdom. Use those points to get at least 1 point in improved judgements so it fits to a 9 second cool down. Spend the rest of the points in the ret tree to improve your own threat and/or the raidwide dps - exactly where in the ret tree is somewhat dependant on the usual group you raid with, different players and specs contribute with different buffs and debuffs to a raid.
Get the armour trinket from triumph emblems (glyph of indomisomething) to replace your dodge/armour trinket
Replace the parry gem in your leggings with 30 stamina, as a general rule only gem for something other than stamina if : you are short on defense - you need to activate your meta gem - you want to get a socket bonus
And just for the heck of it : Max out your professions, the buffs you get from those are not wasted at all