Thanks to player reports and feedback, we’ve identified a bug affecting how XP was calculated for parties of 6 or more players.
We are rolling out a hotfix right now, to all realms, that should correct this. Going forward, XP awarded should be significantly lower for parties of 6 or more players.
Again, thank you very much for your feedback.
Just want to note that this fix is not a tuning adjustment or balance change.
In original WoW, there was an XP penalty while in a group of 6 or more players. A contemporary bug had scrambled the penalty, and that bug is now fixed.
Again, we really appreciate the player reports that brought it to our attention.