To clarify, there wasn't an intentional reduction in the number of herb spawns. We're investigating the situation now.

Update: I spoke too soon. I'll have more information for you soon.

11/28/2012 12:08 PMPosted by Sweatpants

What the hell is up with this nerf? I've been flying around Briny Muck for around 30 minutes and I've found maybe 10 nodes, and that's 10x more than I found in dread wastes.

Update: I spoke too soon. I'll have more information for you soon.

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.