That farming guide probably works just fine - anchor weed shares nodes with other herbs so you have to pick a lot of the other herb to get anchor weed to spawn and if someone else is out there as well they might pick the anchor weed that you trigger to spawn before you even see it.
I am surprised you are using anchor weed for healing potions though - I have two alchemists and I am pretty sure they don’t use anchor weed.
I will pick something like 1000 herbs…and only have (give or take) 100 anchors…its crazy. just keep picking…what I have noticed tho is that river bud is better at spawning anchors, than sea stalks
I tired that loop and got one herb in an hour. Maybe its just my luck or something. 
I needed anchor weed to make flasks to get to 150, but im not sure you cant skip those now. I was 150 when the new stuff came out.
As everyone else said, it replaces ground herbs, so riverbud, akundas bite, winters kiss. I get a surprising amount in mechagon, too. Does not spawn from zin’anthid though so Nazjatar won’t have any.
On my realm, at least, I’m seeing a lot fewer herb nodes spawning. I don’t know if Blizzard turned down the spawn rate, or if it’s tied to population, buy my old routes are looking pretty bare these days.
Anchor weed is totally RNG in herbing nodes. I have a tendency (or at least in my experiences anyway) to find more around water than anywhere else. But even then I can dedicate HOURS and maybe if I’m lucky find 6 nodes total in that time… That is also a day when I’ll go buy a lotto card.
Make sure you’ve done all of the quests to maximize your collection efforts, that is the most important thing of all… If you’re still only getting 2 per pick, get to it and get waycrest done… (Treatise on Anchor Weed)…
The best routes will be kept secret for maximum profit. 
I’d wager it’s because players have returned with 8.2, no matter what the naysayers claim, and they are all flying around now, so nodes will be gone as soon as they show up.
I just wait for the WQ that rewards anchor weed and then I do it on like 10 alts.
I do the WQ that give Anchor Weed. Also added the follower items that gave herbalist mats.
I’m flying, too, and even when I don’t see any other players in the area, or nodes despawning ahead of me, I’m only finding about 1/3 of the nodes I’d expect to find. Generally when I’m harvesting, I at least see traces of other players on the route; now, I’m seeing neither players nor herbs. It’s just been very odd since the patch dropped.
This. This right here.
Those farming maps on wow professions while okay, are not the best routes.
Just pay attention and learn your own route and you will find better spawn rates.
Is why I’m trying to get alchemist up there as the new healing potion at level 120 is 133k or about half health for one potion.
Thankfully as an Alchemist I can make 10 to 15 of them a day through transmutation 
Its a little RNG. And I definitely pick everything I see. I may find 1-2 nodes in one hour. Next hour I could find 15 nodes.
wow-professions, great resource usually when it comes to farming stuff.
At least where to farm the stuff.
You see the full routes they provide?
Break them down into smaller chunks,
herbs respawn every couple of minutes, so you want your farming
laps to hit those respawns.
LFG Anchor Weed farming groups are common,
but, more often than not, you need to be a druid,
yes, yes, Horde bias, Taurens quick herbing
Or just get herbalism enchant on gloves.
Your local economy can thank me later
If you’re a dual-gatherer on something not high-mountain tauren,
get the darkmoon firewater.
1Hr super gathering awesomeness.
Just like everything else in WoW… you wait until Anchor Weed is a reward for turning some other random junk in… and then you push all your alts through and walk away with a ton.
World of Exploitingaltscraft. This is the new game and how to play it.
To find the anchor weed, you must think like the anchor weed. When you seek out the weed of anchors, ask yourself this question: “If I were an anchor weed, where would I grow?”
joking aside, I don’t use any farming guide. I just find an area that has a lot of ground herbs and run around that. Anchor weed has a chance to spawn from any BfA herb that’s on the ground. For Kul’Tiras, that’s riverbud, sea stalks, and winter’s kiss. For Zandalar, that’s riverbud, sea stalks, and akunda’s bite. Just find an area where most of the herbs are on the ground, and plan out a route and run it for about 30 mins to an hour. My favorite route is around Norwington Estate in Tiragarde Sound. I do laps around that, and usually come out with about 50 or so Anchor weed in a 30 minute run.
I remember back in Uldir it was fairly common to see Anchor Weed groups in like Drustvar or Nazmir where people spread out and then collapsed when someone found one. Probably even easier with flying.
I heard they nerfed the spawn rate in 8.2. Don’t quote me on that though. It works on RNG with causing it to spawn in place of another herb so lots have to be constantly picked. I’m absolutely shocked to see stacks of 200 of Anchor Weed, lol.
So Blizz just being Blizz.