I thought I'd go over here the different types of gear that are available for paladins and how we can put them together into different sets. In general, paladins who have been tanking for quite a while have collected several different sets of gear for different purposes, though a lot of new paladins might not know quite what they are talking about. I'll go through those different sets and the kinds of priorities we make for each of those sets of gear.
The Avoidance Set
The avoidance set is one that focuses on avoiding as many attacks as possible. It tends to be used on really hard hitting bosses, where extra health won't protect us. For example, if something's hitting me for 28k per hit, no extra health will help me survive a second hit. For this set, we're looking for, in order:
Why armor? It doesn't help us dodge, but it makes us easier to heal. While dodge/defense/parry items are best for this kind of set, a little extra armor can help us recover more quickly those times we are hit.
The Dragon Set
What I call the "dragon" set is a set that is used when facing high amounts of magical damage. Basically, it's about stacking hitpoints, hitpoint, hitpoints. Hitting the block cap is nice, but at the end of the day, you want to be able to absorb big breaths. The goal with this set is to be able to absorb huge breaths or spells so that your healers have time to heal you up. This was the big set during the tough fights of early Wrath like Malygos, Sartharion and Sapphiron. Now, it's useful for fights like Razorscale and Ignis.
The priority for this set is:
The Block Set
This threat serves as our threat set and our AoE tanking set. It's also nice for any trash that doesn't hit like a truck (there are a couple bits of trash that do; you'll get used to which ones). Basically, you want to use this where you're offtanking adds that don't have a skull over them, like adds on Deconstructor or, especially, Thorim. It's also great for fights where you spend a lot of your time dpsing. The goal is to maximize survivability on small hits by maximizing block value and then maximize threat by maximizing block value and strength. Putting together a good block set takes a lot of time and effort, as there is often only one suitable piece per slot.
The priority for this set is:
The Mixed Set
A lot of bosses and fights don't require a special set of gear. Sure, the boss might kill you in two hits, so dodge is good, or it might kill you in three hits, so some more stamina is helpful. You need to hold aggro, but it's not an insane dps race. The mixed set is a set I like to use for day-to-day use. Unless something hits exceptionally hard or exceptionally lightly or breathes on me, this set is the one I wear. It's good to be block capped in this set, to get rid of streaks.
There isn't really a priority for this set. I like to think of this set using a point system:
Dodge, Defense, Agility, Stamina and Armor are all valued at their full item value (1 dodge/def/agility=1.5 stamina=14 armor). Parry's a little lower, just because it doesn't scale as well. Hit and Strength are valued at about half, because threat is nice, but not overwhelmingly important right now.
Those are my four sets that I use for various things. Of course, on occasion, I'll mix things up. For example, a particular boss might require me to generate almost no threat at all, like the second boss on the Iron Council, I'll value strength at 0. If another fight requires taunting to share a boss, I'll value hit more. And so forth. However, these are my standard outfits, and I hope you find them helpful.