The new Tier 13 armor drops only from bosses in the lead up and including the final battle with BossDeathwing, There will be three sub-tiers to Tier 13 pieces: Looking for Raid (Raid Finder), Normal and Heroic. as part of Patch 4.3.
Blood, 2P—When an attack drops your health below 35%, one of your Blood Runes will immediately activate and convert into a Death Rune for the next 20 sec. This effect cannot occur more than once every 45 sec.
Blood, 4P—Your Vampiric Blood ability also affects all party and raid members for 50% of the effect it has on you.
DPS, 2P—Sudden Doom has a 30% chance and Rime has a 60% chance to grant 2 charges when triggered instead of 1.
DPS, 4P—Runic Empowerment has a 25% chance and Runic Corruption has a 40% chance to also grant 710 mastery rating for 12 sec when activated.
Balance, 2P—Insect Swarm increases all damage done by your Starfire, Starsurge, and Wrath spells against that target by 3%.
Balance, 4P—Starsurge generates 100% extra Lunar or Solar energy while Eclipse is not active.
Feral, 2P—Pulverize now also grants your Mangle (Bear) critical strikes a 100% chance to trigger Savage Defense, and your Blood in the Water talent now causes Ferocious Bite to refresh the duration of your Rip on targets with 60% or less health.
Feral, 4P—Frenzied Regeneration also affects all raid and party members. This effect cannot be triggered if you have been in Bear Form for less than 15 sec. In addition, your Stampede talent now grants two charges after using Feral Charge (Cat).
Restoration, 2P—After using Innervate, the mana cost of your healing spells is reduced by 25% for 15 sec.
Restoration, 4P—Your Rejuvenation and Regrowth spells have a 10% chance to Timeslip and have double the normal duration.
2P—Your Arcane Blast has a 100% chance, and your Fireball and Frostbolt spells have a 50% chance to grant Stolen Time, increasing your haste rating by 50 for 30 sec and stacking up to 10 times. When Arcane Power, Combustion, or Icy Veins expires, all stacks of Stolen Time are lost.
4P—4P -- Each stack of Stolen Time also reduces the cooldown of Arcane Power by 7 sec, Combustion by 4 sec, and Icy Veins by 6 sec.
Healer, 2P—After using Power Infusion or Divine Hymn, the mana cost of your healing spells is reduced by 25% for [10|23] sec. (10 sec for Discipline, 23 for non-Discipline.)
Healer, 4P—Your Power Word: Shield has a 10% chance to absorb 100% additional damage and increase the mana granted by Rapture by 100%, and the duration of your Holy Word abilities is increased by 20%.
Shadow, 2P—Shadow Word: Death deals an additional 55% damage, and reduces the damage you take from your own Shadow Word: Death when the target fails to die by 95%.
Shadow, 4P—Your Shadowfiend and Shadowy Apparitions have a 100% chance to grant you 3 Shadow Orbs each time they deal damage.