Per MMO-Champion.

Tier 8 Bonus
Death Knight

* Death Knight T8 Melee 2P Bonus -- Increases the critical strike chance of Death Coil and Frost Strike by 5%.
* Death Knight T8 Melee 4P Bonus -- Increases the bonus damage done per disease by 20% on Blood Strike, Heart Strike, Obliterate, and Scourge Strike.
* Death Knight T8 Tank 2P Bonus -- Increases the damage done by Rune Strike by 5%.
* Death Knight T8 Tank 2P Bonus -- Increases the damage done by Rune Strike by 10%.

Druid

* Druid T8 Balance 4P Bonus -- Each time your Insect Swarm deals damage, you have a chance to make your next Starfire cast within until cancelled instant.
* Druid T8 Balance 4P Bonus -- Each time your Insect Swarm deals damage, it has a chance to make your next Starfire cast within 10 sec instant.
* Druid T8 Feral 2P Bonus -- The periodic damage dealt by your Rake, Rip, and Lacerate abilites has a chance to cause you to enter a Clearcasting state.
* Druid T8 Feral 4P Bonus -- Increases the duration of Savage Roar and Survival Instinct by 8 sec.
* Druid T8 Restoration 2P Bonus -- Increases the healing done by your Swiftmend spell by 10%.
* Druid T8 Restoration 4P Bonus -- Your Rejuvenation spell also instantly heals your target for its periodic healing amount.

Hunter

* Hunter T8 2P Bonus -- Increases the damage done by your Serpent Sting by 10%.
* Hunter T8 4P Bonus -- Your Steady Shot has a chance to grant you 600 attack power for 15 sec.

Mage

* Mage T8 2P Bonus -- Your Arcane Blast, Frostbolt, Frostfire Bolt, and Fireball spells have a chance to grant you 350 spell power for 15 sec.
* Mage T8 4P Bonus -- You have a chance for the effect of your Missile Barrage, Hot Streak, or Brain Freeze talent not to be consumed when you cast the spells which benefit.

Paladin

* Paladin T8 Retribution 2P Bonus -- Increases the damage done by your Exorcism and Hammer of Wrath abilities by 10%.
* Paladin T8 Retribution 4P Bonus -- Increases the critical strike chance of your Divine Storm and Crusader Strike abilities by 10%.
* Paladin T8 Protection 2P Bonus -- Increases the damage done by your Seals by 10%.
* Paladin T8 Protection 4P Bonus -- Shield of Righteousness now increases your shield block value by 225 for 3 sec.
* Paladin T8 Holy 2P Bonus -- Your Holy Shock critical heals now also place a periodic healing effect on the target, healing for 15% of the Holy Shock's heal amount over 9 sec.
* Paladin T8 Holy 4P Bonus -- Increases the damage absorbed by your Sacred Shield by 10%.

Priest

* Priest T8 Shadow 2P Bonus -- Increases the damage done by your Devouring Plague by 15%.
* Priest T8 Shadow 4P Bonus -- Your Mind Blast also grants you 15 haste rating for until cancelled.
* Priest T8 Healer 2P Bonus -- Increases the critical heal chance of your Prayer of Healing by 10%.
* Priest T8 Healer 4P Bonus -- Casting Power Word: Shield also grants you 15 spell power for until cancelled.

Rogue

* Rogue T8 2P Bonus -- Your Deadly Poison causes you to gain 1 energy each time it deals damage.
* Rogue T8 4P Bonus -- The damage dealt by your Rupture can now be critical strikes.

Shaman

* Shaman T8 Enhancement 2P Bonus -- Increases the damage done by Lava Lash and Stormstrike by 20%. (0 yd, cast: 0 seconds, val1: 20)
* Shaman T8 Enhancement 4P Bonus -- Increases the frequency of Maelstrom Weapon being triggered by your melee weapon attacks by 20%.
* Shaman T8 Restoration 2P Bonus -- Reduces the cooldown on Riptide by 1 sec.
* Shaman T8 Restoration 4P Bonus -- Reduces the cast time of Chain Heal by 0.2 sec.
* Shaman T8 Elemental 2P Bonus -- The periodic damage dealt by your Flame Shock can now be critical strikes.
* Shaman T8 Elemental 4P Bonus -- Your critical Strikes from Lightning Bolt cause the target to take nature damage equal to 8% of the Lightning Bolt's damage over until cancelled sec.

Warlock

* Warlock T8 2P Bonus -- Increases the damage done by your Unstable Affliction and Immolate spells by 20%.
* Warlock T8 4P Bonus -- Increases the critical strike chance of your Shadow Bolt and Incinerate spells by 5%.

Warrior

* Warrior T8 Protection 2P Bonus -- Increases the critical strike chance of your Devastate ability by 10%.
* Warrior T8 Protection 4P Bonus -- Shield Block also grants you 20% reduction to magical damage taken.
* Warrior T8 Melee 2P Bonus -- Heroic Strike and Slam critical strikes have a chance to grant you 150% haste rating for 5 sec.
* Warrior T8 Melee 4P Bonus -- Increases the critical strike chance of Mortal Strike and Bloodthirst by 10%.

wow those bonuses look kind of sexxy for shadow priests. The new talent has DP hitting for 15% OF total dmg AND increases total dmg by 15% plus this set bonus increasing it by 15% and as long as the DK's still spread it around for us we'd have some FUN

Meh.

Ret's bonuses are bland, boring, and unspired, but at least they're mediocre buffs. 10% to DS and CS crit isn't that big of a deal since you're running with 40%+ in raids with buffs anyway.

Prot's 2pc is substandard, considering SoV can tick for a whopping 10, making the bonus give it a boost to - ready? - 11.

Holy's 2pc would be fantastic if it didn't hinge on pure RNG. HoTs are nice - controllable HoTs are useful. Since Shock crits will average around 10k in T8, that's a 1500 HoT. Not bad, but not noticeable, either. And 10% to SS? So an extra 250 in a raid where MTs have 40k HP and get his for 25k? Yay.