I made this Stormvine farming guide to help out players who want to farm the herbs instead of buying them from the Auction House. Stormvine requires 425 Herbalism to gather and it can be a tricky herb to gather as it doesn't spawn a lot.
Vashj'ir - Shimmering Expanse
This is the best place to farm Stormvine. Respawn rate is fast and you can also get a lot of Azshara's Veil.
Vashj'ir - Abyssal Depths
If someone is already farming at Shimmering Expanse you can go to Abyssal Depths because it is also a great place for farming.
If you don't like the underwater zones, you can go to Mount Hyjal and gather Stormvine there.