Diablo 4's Season 5 patch notes will include a before and after comparison for changes to Unique and Mythic Unique items as "there are changes to nearly every single one."
We've had an inkling of the wide scope of Season 5's PTR since the June Campfire chat revealed a new endgame roguelite mode and boss, new Uniques, and massive quality-of-life changes including re-playable bosses. However, the full patch notes are still to come, and according to global community development director Adam Fletcher, they'll include changes for almost every Unique and Mythic Unique item in the game.
