On top of general class changes Shadowlands Season 4 also has a wave of PvP-only class changes. Those changes include another round of nerfs to Holy Priests, Affliction Warlock balancing, among other class changes.
With the new season, you’ll see increased item levels for rewards and new seasonal rewards. The new seasonal rewards for PvP include a new Arena title: “Eternal Gladiator”, a new weapon illusion:
