from WoW 5.4 PTR blog (I would have added the link but I am unable to)
I underlined the new changes added today.
The debuff from using a Demonic Gateway has been increased to 60 seconds (up from 15 seconds).
Fel Armor no longer reduces all damage taken by 10%.
Fel Flame now deals 13% more damage, costs 2% less mana, and no longer increases the duration of damage-over-time spells.
Rain of Fire now has a reduced chance to generate Burning Embers.
Howl of Terror is no longer a talent and is now a baseline skill for all Warlocks.
Demonic Breath, a new talent replacing Howl of Terror. The Warlock sends out a cone of Shadow damage, snaring targets, has a 20-second cooldown.
Kil'jaden's Cunning no longer reduces movement speed, and will now allow the Warlock to cast Incinerate, Malefic Grasp, and Shadow Bolt while moving. is no longer a passive ability. Kil'jaden's Cunning now has a duration of 15 seconds with a 1.5 minute cooldown.
Mannoroth's Fury is no longer a passive ability. Mannoroth's Fury now has a duration of 10 seconds with a 60 second cooldown, and increases the area of area-of-effect by 500% and increases damage by 100% for Hellfire, Immolation Aura, Rain of Fire, and Seed of Corruption.
Soul Leech can now also activate from Shadowburn, and caps out at 15% of the Warlock and their pet's maximum health (down from 100%).
Most of these were expected except for the Gateway nerf and the Soul Leech nerf (again). 60 sec debuff duration is going to really hurt PVP and maybe 2 raid encounters (H Meg and to a lesser extent H Lei Shen). Soul Leech getting nerfed from 30% to 15% is harsh as well but this was expected to a certain extent.