Mining and Herb spawn rates in Pandaria have been reduced by approximately 50% in patch 5.1, and this is indeed an intended change. These are in addition to the hotfix that was applied in 5.0.5 to lower the spawn rate of Ghost Iron. In all of these cases, the reduction was prompted because the resources were too abundant, resulting in ore and herbs being undervalued, and also therefore the effort that our herbalists and miners put in to collect each node. We’ll be monitoring the situation, though, and should the current rates prove to be too low then we’ll make further adjustments as necessary. Latest blizz post on that thread.
