Blizzard have nerfed Plunderstorm experience gains in Duos, as players were leveling too quickly after yesterday's Plunder increases.
Players get experience every 25 Plunder and thus after yesterday's Plunder increases, players were leveling much faster than originally intended. This has been addressed in Duos as players could level to 10 very quickly and dominate the rest of the lobby.
This change has no impact on renown.
Blizzard
Avast there!
After our changes yesterday to increase the amount of plunder you get in a match, we saw an unintended side-effect: players were leveling quicker in duos than expected! Plunder gold piles picked up in Plunderstorm contribute towards the overall amount of experience you gain during a match, especially thanks to a bug at level 3.
When leveling up in a match is too fast, some teams get ahead of others much quicker which can lead to less competition. Players hitting max level too early can remove the sense of power progression for the rest of a match, as well.
So this evening, we’ve deployed a hotfix to straighten that all out.
Read more on wowhead.com