If they increase the spawn rate, the price of herbs and consumables would absolutely tank.
Don’t farm herbs unless you have epic flying and access to an hour of the day when very few people are on.
In fact, don’t farm anything. Do dailies. Do the quests. Buy materials from the AH and craft them for a profit.
I haven’t farmed anything this expansion and on a fresh account I’m doing just fine. Was leather working and skinning and now LW and herb. But cooking and LW has made me a fortune. I only picked up herb when I got epic flying, and it’s terrible unless you get a good time on mana thistle spawns and carefully set a timer to keep picking them. But that is rare and herb has been the absolute lowest income % wise compared to dailies, quests and crafting for profit.
Now that I have a lot of gold, I buy raid consumables when they’re 2-3g cheaper and sell them at higher prices when it’s raid day for most of my server. That and controlling markets where there is a very limited supply, like dark runes and scrolls of strength and agility
Also, just tip a blacksmith or alchemist to make stuff and sell it on the AH. Figure out that if you craft 40 potions, you’ll get 20% extra potions/elixirs on average, and tip the person 10% of whatever your profit gains would be. Easy money, no professions required. The overhead gold comes from just doing quests or dailies.
100 agility elixirs from raw mats netted me 360 gold in profit and were easy to sell, so I tipped an alchemist 35g to craft them. They instantly invite when I make a post that I’m tipping that much. Everyone’s happy. 10 minutes of time invested.
I hate farming. It’s brainless and boring. You don’t have to farm anything to have everything you want in this game. Have everyone else do that crap for you. Figure out how to make profits through crafting. It requires one thing: some gold through questing or dailies. No professions required. There’s no way everyone’s listing crafted goods on the AH cheaper than the cost of the materials. Maybe some of them, but not all of them.
Didn’t grind a thing. Craft stuff or have people craft and you’ll be there in no time. It doesn’t take much knowledge compared to manipulating and controlling markets. Use TSM (just download and use it without Configuring a thing) or manually add up how much it would cost to craft something compared to what it sells for, and you’re good to go 
TSM is INCREDIBLY helpful though. It shows how many of an item sells a day. It shows you how much profit you’ll make per item based on crafting one and selling it too. So if only 60 pieces of food sells a day on average, then you don’t want to make 10 stacks. You’ll relist them so many times you’ll hate yourself. Maybe 1-2 stacks. Find the stuff that sells a lot every day, like 100-400 a day and make a ton of those instead.