Blizzard has now confirmed that no tier Shoulders or Chests will drop from the Great Vault during Week 1. In addition, killing a raid boss that drops tier will increase your chance of receiving tier in that slot. The Tier Bosses in Sepulcher of the First Ones are:
Hands: Lihuvim Pants: Halondrus Helm: Anduin Shoulders: Lords of Dread Chest: RygelonThe Tier Shoulders and Chests will not be available week 1 as the bosses are not available. Thus, it makes sense that Tier Shoulders and Chests cannot drop in the Great Vault during Week 1. This is a change from on the PTR, where the Great Vault was dropping all pieces of Tier. In addition, Blizzard announced that killing a Tier boss will increase the chance of seeing the related Tier piece in the raid row of the Great Vault.
Birds: Don’t leave yet! Will we be able to get the new, higher item level gear next week? Or is it staying at 252 next week. I’m still here Birds!Mythic+ end-of-run drops will cap at Mythic+10 throughout the week of March 1–7, and Season 3 Rated PvP gear upgrades are initially capped at Rival II (base item level 268) until Mythic Difficulty Sepulcher of the First Ones is available.Completing the Great Vault participation requirements next week, March 1–7, will reward the new item level thresholds in the March 8 Great Vault after the weekly maintenance.Season 3 Great Vault RewardsDifficultyEnd-of-RunMissed TimerGreat VaultMythic+15ilvl 262ilvl 259ilvl 278Class set pieces, excluding shoulder and chest, will appear in the Great Vault rewards starting on March 8 from all vault categories. Defeating raid bosses that drop tier will increase your chances of receiving that tier slot from the Raids row. The shoulder and chest pieces will appear in the Great Read more on wowhead.com