The hotfix is already live. Blizzard deployed it on November 8 at about 19:05 UTC, and community manager Kaivax specified that the bonus applies to experience earned from killing enemies inside dungeons.

Blizzard gave one reason in the official forum post: repeat runs should feel more worthwhile for leveling.

World of Warcraft: Forever has nine new five-player dungeons spanning levels 13 through 60. That makes the bonus relevant through most of the leveling path. Our launch report covers the rulesets, subscription access, and the first raid schedule.

The game is available on PC. Its test history and upcoming dates are listed on the World of Warcraft: Forever page.