As a Paladin you get to choose from 3 sets for PVP rewards.
- Ornamented (+healing)
- Lamellar (+spell damage and healing)
- Scaled (Str, Stam, Crit)
I'm going to ignored Scaled for the time being.
The 2 piece set bonus on each set is +35 resilence.
The 4 piece set bonus is reduced cooldown on Hammer of Justice.
One idea is to mix two pieces from one set with 3 pieces from the other. This gives you an extra 35 resilience because you get both sets 2 pieces bonus.
What do you give up for that 35 Resilience.
Lets examine an example set of Ornamented Shoulders, Legs, and Gloves with Lamellar Helm and Chest.
The difference over a 5/5 Ornamented Set is:
+65 Spell Damage
+14 Spell Crit
Well you gain more than just the set bonus. You actually gain 39 resilience because the two Lamellar pieces have 4 more than the Ornamented Pieces (1 more on the head, 3 more on the chest). You also gain 65 spell damage and 14 Spell Crit.
So what's the price? What do you lose over going 5/5 Ornamented?
47 +healing and 12 intellect. I would argue the spell crit helps make up for some of the lost +healing.
In my mind the trade is well worth it.
So far Arena points, I recommend
Merciless Gladiator's Ornamented Gloves
Merciless Gladiators Ornamented Spaulders
Merciless Gladiators Ornamented Legplates
Merciless Gladiator's Lamellar Helm
Merciless Gladiator's Lamellar Chestpiece