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.
Will Shadow Word: Death now be used above 25% health? I think the 4 set bonus is a joke. It feels like they are removing one of the things that made Shadow Priest DPS fun: adapting to what buffs you have.