In the latest Dragonflight Beta build, Blizzard nerfed the item level of gear from Primalist Invasions.
Primalist Invasions are world events in Dragonflight that will be available in Season 1. They offer two currencies that can be exchanged for PvE gear in Valdrakken.
Primalist Invasion gear sold my Mythressa was Item Level 382 before the change.
However, it got nerfed to Item Level 359. You can farm an unlimited amount of Elemental Overflow each week when Dragonflight Season 1 starts. The item level is on par with Heroic Dungeon gear.
Rethelshi sells a more powerful type of PvE gear for Storm Sigils called Primal Infused gear. You can only farm four sigils per week, so it will take a long time to unlock the whole set for your character. Before the change, Primal Infused gear used to have item level 395.
In the new Dragonflight Beta build, the gear is only item level 385, which is on par with Raid Finder difficulty. To buy Primal Infused equipment, you must also own the blue gear pieces from Mythresa.
