While there's been no comment from Blizzard on the matter, it appears that the respawn rate of some herbs has been drastically increased since patch 4.0.6. Now that the Undermine Journal is working again, we can actually see this in effect! Go ahead and search for Whiptail on any realm you want, and scroll down to the second graph under the "Price and Availability History" section.
Most realms' herbalists have noticed this change and have been herbing their hearts out. If this does not change, we can expect a drastic reduction in prices for all inscription- and alchemy-based products that require Volatile Life or herbs. I haven't seen as drastic an increase in other herbs that Whiptail, but Volatile Life, at least, will be cheaper while this lasts. Also, herbalists I've talked to are saying that all the herbs in Deepholm and Twilight Highlands are respawning faster, but that hasn't translated to anything I can measure yet. The way they're describing this, though, is that it feels like it did before the Dec. 8 hotfix that reduced the number of nodes.
Many of the realms I've looked at so far are showing a trend of increased supply without the decrease in price, but that's mostly because herbalists haven't started to see unsold auctions. If the supply continues to come in at this rate, the farmers will start undercutting each other harder.
If you want to take a look at other realms, the fastest way it to scroll down to the "Other Markets" section on the page:
Clicking on any realm will bring you to the results for that server.
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