Before you say anything like....yeah that'll take a long time to do since gromsblood isn't an easy herb to gather. I say only takes 30 minutes of your actual game time! Check this out!
First we will want to get to Desolace, as this is the place this whole guide is based on. I was running around Desolace one day trying to farm gromsblood and then it hit me, like a ton of bricks! So, that's where the idea for this guide came from. Ok, on with the guide!
There really is only one area in Desolace that has nodes of gromsblood available. In the middle of this is a pool of water and that's where we will start. It's simple really all you will do starting at the pool is run around the structures (mountains, hills, etc.) that surround the pool. You can usually get anywhere from 1-3 gromsblood from each node. Also, I have never really experienced more than 4 nodes of gromsblood in this area.
After you collect the different nodes of gromsblood, then logout and wait about 15-20 minutes (remember I said it would only take 30 minutes game time!) This 15-20 minutes makes it a good time to get a bathroom break, clean some house, or surf your favorite website! Ok, ok....shameless plug!
The last obvious step I guess is to rinse and repeat!