In their newly released Season of Discovery Phase 4 announcement, Blizzard has revealed that Raid Openings will be staggered and not initially available at Phase 4 launch on July 11th. Instead, they will have dedicated Global Release times in the weeks after launch.
Experience Lord Kazzak and Azuregos on July 18 at 1:00 p.m. PDT globally as brand-new instanced versions of these encounters. These encounters can be experienced with up to 40 players but will be tuned as 20-player content, making them both pick-up-group-friendly with 40 players, but also giving players the option to maximize their rewards by attempting them with 20-players.
Prepare to take on Ragnaros and Onyxia in their lairs on July 25 at 1:00 p.m. PDT globally.
Experience Molten core as a 20-player dungeon with 10 classic bosses (+1,) revamped loot, redesigned Tier 1 sets, and more. Players will also be able to turn up the heat with a new variable difficulty mechanic allowing players to earn more rewards from undertaking a higher difficulty. Don’t forget your fire resist gear! You are going to need it. We’ll be adding one more surprise to this classic raid dungeon for intrepid adventurers to discover.
According to Blizzard, World Bosses such as the new instanced versions of Lord Kazzak and Azuregos will be available after the first weekly reset on July 18th at 1 pm PDT, while Molten Core and Onyxia's Lair will be delayed an additional week until July 25th.
Originally, Molten Core and Onyxia's Lair were both available on launch when Classic WoW was released in 2019. This staggered release is a departure from that original timeline, while it remains in line with similar recent decisions to stagger the Raid Release times for Cataclysm Classic.