PvP scaling

PvP scaling is a PvP game mechanic introduced with Battle for Azeroth. It adjusts the damage dealt to enemy players as well as healing to friendly players while engaged in PvP combat to partially compensate for gear item level differences between players. It is only applied to players between levels 110 to 120 and is intended to reduce the power gains acquired from gear in PvP, but not completely negate it.

It is applied in all PvP activities such as world PvP, arenas, battlegrounds and duels.

In-depth explanations
When player A deals damage to player B, the game server adjusts the damage dealt by a coefficient computed from player A character level, player A equipment item level, player B character level and player B equipment item level.

If player A and player B are both level 120 and have exactly the same item level in every equipment slot, then the scaling coefficient is 1 and no scaling occurs. Otherwise, damage scaling will occur and player A will see unscaled damage in his combat log whereas player B will see the scaled damage in his combat log.

The scaling coefficient can be determined by dividing the damage seen by player B by the damage seen by player A.

Scaling applies equally to all sources of damage including auto-attack, class abilities, consumables and trinkets.

Example
Player A is a veteran, well-geared level 120 character and player B has just hit 120 and barely has any gear.

Player A casts Fireball on player B and sees 10000 damage on his screen and combat log.

Player B sees on his screen and combat log that this Fireball has actually dealt 8000 damage to him.

Player B health is reduced by 8000 and we can deduce the scaling coefficient of player A against player B is

Scaling coefficient of player B against player A will be the inverse:

Player B then retaliates with his own Fireball which only deals 6000 damage. Player A will actually take 7500 damage:

Additional information
The following information has been discovered through in-game testing:
 * Buffs or class modifiers (such as passive tank health increase) do not affect the scaling coefficient.
 * Only equipped gear is considered for PvP scaling; items held in bags or bank do not affect the scaling coefficient.
 * Scaling helps the under-geared player, up to a minimum item level of 286 in the equipment slot at level 120. For this reason, players should never go in PvP with empty equipment slots. This can be verified in-game with  while being naked: the third value which corresponds to PvP item level will be 286.
 * Equipment slots are weighted to compute scaling coefficient. For example, weapon slot contributes more and ring slots contribute less to the final scaling coefficient.
 * Different items with the same item level in the same equipment slot will result in the same scaling coefficient regardless of the presence of enchantments or minor attributes such as Leech, Speed and Avoidance.
 * Gems do contribute to the scaling coefficient (an empty gem socket doesn't). Gems previously didn't contribute to the scaling coefficient due to the abuse of players equipping low-level gear with many gem slots, this has been hotfixed.
 * Damage numbers displayed on battlefield and arena scoreboards are consistent when viewed by different players. It shows the sum of all scaled damage dealt by each player. Healing numbers behave similarly.