Warlocks keep their sacrifice and their demon
Warlocks in World of Warcraft: Forever no longer have to choose between a demon and a sacrifice. 
Demonic Pact keeps the bonus while another demon fights along, Blizzard shows in a new video. The final part also covers Druids and Priests.
The video lasts 8 minutes and appeared on 6 October at 20.20 Belgian time on the World of Warcraft channel. It closes the Class Highlights series, after the first part on the Warrior, the Shaman and the Rogue, and the second part on the Hunter, the Mage and the Paladin.
Part of the Druid changes was already in the first class deep dive. The numbers below come from the tooltips of the beta.
Druid
Like Warriors and Paladins, Druids get more tools to hold threat, says Blizzard. The equipped weapon now raises melee damage in 
Bear Form. Enchantments and procs also work in form, such as Crusader and the 
Windfury Totem of a Shaman.
Lacerate stacks a bleed on the target, and every stack adds 10% weapon damage. Druids can also use consumables in every form. A Bear can drink a Rage potion or a Free Action potion in combat without leaving form.
Cats get more damage on 
Shred, 
Rake and Claw. 
Berserk raises the critical strike chance of abilities that generate combo points by 100%. 
Feral Charge now also works in 
Cat Form, and 
Feral Swiftness now works indoors. Cats can use consumables and weapon enchantments in form as well.
Wrath costs much less Mana, so Restoration Druids can deal damage between heals. In an emergency, 
Wild Growth heals the target and its party over 7 seconds. It also works on members of another party, as long as they belong to the same faction.
Balance gets a simpler 
Eclipse. Every Wrath shortens the cast time of the next 2 
Starfire spells by 0.5 seconds, up to 4 charges. The new talent 
Nature’s Splendor, from level 20, extends 
Rejuvenation, 
Regrowth and 
Insect Swarm. Nature’s Grasp and Entangling Roots now work indoors. With 
Overgrowth, up to 3 enemies can be rooted at once.
Warlock
Affliction loads enemies with damage over time and finishes them with a long Drain, instead of weaving Shadow Bolts in between. The 31 point talent 
Wrack is a channel of 6 seconds. It deals Shadow damage every second and raises the damage the target takes from the other Shadow damage over time effects of the Warlock by 10%.
Destruction gets a tree in which Fire and Shadow spells work together. At the bottom sits 
Incinerate, a Fire spell that deals 25% more damage to a target with 
Immolate on it.
In Demonology, 
Demonic Sacrifice used to cost the bonus as soon as another demon was summoned. Master Summoner and Demonic Sacrifice have been reworked. The capstone Demonic Pact keeps the bonus of the sacrifice when a different demon is summoned. Only summoning the sacrificed demon again still cancels it.
A Warlock can then fight and use 
Soul Link with one demon while keeping the bonus of another. Different pairs serve different builds: Fire damage, Shadow damage, Mana regeneration or survivability, says Blizzard.
Decimation gives Demonology an execute. When 
Shadow Bolt or 
Searing Pain hits an enemy below 35% health, Soul Fire costs no 
Soul Shard for 10 seconds and casts 40% faster. The talent also cuts the cooldown of Soul Fire by 90%.
Priest
Discipline becomes a healer built on shields that prevent damage. 
Penance sits halfway down the tree. It fires a volley of Holy light that heals an ally over time, or deals Holy damage to an enemy.
Holy gets 
Prayer of Mending. It heals an ally the next time they take damage and then jumps to another member of the party. It prefers the party of the target, so it also works when cast on someone in another group.
Shadow gets a rework to become a full damage spec. 
Devouring Plague used to be for Undead Priests only. In Forever every Priest learns it, whatever the race or faction.
Vampiric Embrace can now trigger 
Spirit Tap, for more Mana during a fight. Devouring Contagion halves the Mana cost of Devouring Plague and spreads it to a nearby enemy when the target dies. A hybrid build with Discipline reaches Meditation, for Mana regeneration while casting.
Every talent of the three classes is in the talent calculator, for the Druid, the Warlock and the Priest.
Source: Blizzard Entertainment