Dodge rating is good. Tankadin aggro is a mix of offensive and being-hit spells. If you have enough spell dmg bonus, you can take dodge rating and have plenty of aggro. If you just use Dev aura for more armor not ret (cause it only does 25 (40 with cryst 2 equip bonus), using Sanc blessing, and holy shield, you will reflect dmg on blocks, and for your offensive spells use consecration, seal of righteousness, judgemetn of righteousness. You can judge the enemy with seal of crusader to get each spell (passive and offensive) to be increased by up to 180 spell dmg too), but use this after your first big spell hit on the npc like avenger shield pull or judgement of righteousness.
The "being-hit spells",e.g., ret aura, sanc blessing, holy shield, are there for a tankadin to hold aggro on targets that he is not hitting. It gives tankadin the ability to hold multiple targets but it by no means is the main source of aggro. The offensive spells finish the job to build aggro on the dps target.
If you want to mitigate well, you will get high spell dmg and dodge and parry rating.
Holy shield has 8 charges of blocks, which means in 8 seconds you could potentially generate 200 spell dmg on npc hitting you per block +40ish per same block from sanc blessing, 8 TIMES in 8 SECONDS. Add some dodge and you have good mitigation. It's not a big deal.
Just get 300 spell dmg. Here is my armory. I change gear alot between dmg gear and tanking gear and Fire Res gear so perhaps when you look at it, its my tanking gear -
http://www.wowarmory.com/character-sheet.xml?r=Bleeding+Hollow&n=Embher
By the way, warriors have shield block that raises their shield block rating by 75% passed uncrushable. We have holy shield that makes us uncrushable (assuming you have about 67.1% sum of dodge parry block and miss% from defense and base 5% miss, which is usually gained with about 19% average of each dodge block parry%). However, warrior's shield block only gives 1 block in 5 seconds (2 blocks in 6s with Improved Shield block) and then the 75% block rating increase is lost and they are crushable in the next 5 s (or 6s)until they can use it again.
Tankadin's holy shield has 8 charges in 8 seconds (with improved holy shield), meaning Tankadin is CONSTANTLY uncrushable, while warriors are not. While warriors have 1k more hp, they are getting hit with crushing blows that are 4k more dmg! Crushing blow can be 8k instead of normal partially blocked hit of 4k. AND THEY SAID TANKADIN can't mitigate! YA RIGHT!?
It looks like on bosses that hit more than once in 5s ( twice in 6s), tankadins mitigate more than warriors!