Season of Discovery players have noticed that damage is being reduced in Warsong Gulch against enemy players by 20%, which is an undocumented change that hasn't been mentioned in any Developer communications.
Players on the WoW Forums, Reddit, and elsewhere have been reporting the «bug», but there hasn't been any communication on the change. While Blizzard did create three new helmets, Resilient Mail Coif, Resilient Cloth Headband, and Resilient Leather Mask, that 5% damage reduction is applied on top of the 20% damage reduction already present, making it 25%.
Image credit to Timetorun
While many players suspected Hunter Pets might have been too powerful in Warsong Gulch thinking the damage reduction didn't apply to them, Sarthetv on Twitter did some testing of his own. Based on this data, it means Hunter pets deal 20% less damage to other players, but don't actually reduce incoming enemy player damage, taking the full 100% damage taken! The results are below in the original tweet --
What do you think about flat damage reduction or items to reduce damage taken in Season of Discovery Warsong Gulch?