Blizzard has released Tier 13 Set Bonuses for all classes. Some of the sets you can preview on the official worldofwarcraft page. Please keep in mind that the below data is pre-PTR and could change prior to the release of patch 4.3.
Death Knight
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.
Druid
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 — While Berserk is active, Savage Defense absorbs are 100% larger, 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, and 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.
Hunter
2P — Steady Shot and Cobra Shot generate double the amount of focus.4P — Your Arcane Shot ability has a chance to grant 25% haste to you and your pet for 10 sec.
Mage
2P — Your damaging spells have a 30% 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 — Each stack of Stolen Time also reduces the cooldown of Arcane Power by 3 sec, Combustion by 4 sec, and Icy Veins by 6 sec.
Paladin
Holy, 2P — After using Divine Favor, the mana cost of your healing spells is reduced by 25% for 15 sec.Holy, 4P — Increases the healing done by your Holy Radiance spell by 20%.
Protection, 2P — Your Judgement ability now also grants a physical absorb shield equal to 30% of the damage it dealt.
Protection, 4P — Reduces the cooldown of Divine Guardian by 60 sec and increases the radius of its effect by 70 yards.
Retribution, 2P — Your Judgement ability has a 50% chance to generate 1 Holy Power.Retribution, 4P — While Zealotry is active your abilities deal 12% more damage.
Priest
Healer, 2P — After using Power Infusion or Lightwell, the mana cost of your healing spells is reduced by 25% for [10|15] sec. (10 sec for Discipline, 15 for non-Discipline.)Healer, 4P — Your Power Word: Shield has a 10% chance to absorb 100% additional damage, and the cooldown of your Holy Word abilities is reduced by 20%.
Shadow, 2P — Shadow Word: Death deals an additional 55% damage, and you no longer take damage from your own Shadow Word: Death when the target fails to die.
Shadow, 4P — Your Shadowfiend and Shadowy Apparitions have a 100% chance to grant you 3 Shadow Orbs each time they deal damage.
Rogue
2P — After triggering Tricks of the Trade, your abilities cost 20% less energy for 6 sec.4P — Increases the duration of Shadow Dance by 2 sec, Adrenaline Rush by 3 sec, and Vendetta by 9 sec.
Shaman
Elemental, 2P — Elemental Mastery also grants you 400 mastery rating 15 sec.Elemental, 4P — Each time Elemental Overload triggers, you gain 200 haste rating for 4 sec, stacking up to 3 times.
Enhancement, 2P — While you have any stacks of Maelstrom Weapon, your Lightning Bolt, Chain Lightning, and healing spells deal 20% more healing or damage.
Enhancement, 4P — Your Feral Spirits have a 45% chance to grant you a charge of Maelstrom Weapon each time they deal damage.
Restoration, 2P — After using Mana Tide Totem, the cost of your healing spells are reduced by 25% for 15 sec.
Restoration, 4P — Increases the duration of Spiritwalker’s Grace by 5 sec, and you gain 30% haste while Spiritwalker’s grace is active.
Warlock
2P — The duration of your Doomguard and Infernal summons is increased by [15|45] sec and the cooldown of of those spells is reduced by 4 min. (45 for Demonology, 15 for non-Demonology.)4P — Soulburn grants a 10% increase to your spell power for 10 sec.
Warrior
Protection, 2P — Your Revenge ability now also grants a physical absorption shield equal to 20% of the damage done by Revenge.Protection, 4P — Your Shield Wall ability now grants 50% of its effect to all party and raid members.
DPS, 2P — Heroic Strike costs 10 less rage while Inner Rage is active.
DPS, 4P — Your Execute critical strikes have a 20% chance to refresh the duration of Colossus Smash.