Everyone knows the quest Plants of Zangarmarsh Quest: Plants of Zangarmarsh - Thottbot: World of Warcraft that turns into the rep quest Identify Plant Parts Quest: Identify Plant Parts - Thottbot: World of Warcraft. I have found a few mobs that drop the most frequently. I tested this by killing 20 of each mob and seeing how many dropped.
Mob: Mudfin Frenzy (The fish in the water lol...) they have a 25.5% drop rate, 1.3k hp and from level 60-63.
After killing 20 I got 11/20 1 green 3 grays and 7 items called Grime-encrusted Scale that sells for 8 silver and 70 copper. Not only was this one of the fastest but I also got some good cash XD
Mob: Feralfen Hunter (You'll see these south of the Twin Spire Ruins in Zangarmarsh) they have a 28.6% drop rate, 4.2k hp and from level 61-62.
I killed 20 and only got 7/20. They drop atleast 6 silver per kill and got 0 greens and 2 grays. Not the best but could be better than the fish if you need more money.
Mob: Bogstrok Razorclaw (These are north of the Spawning Glen and West of Zabra'Jin) These have a 34.7% drop rate, 5.5k hp and they are from level 62-63.
This was my final test and I killed 20 and got 14/20. They don't drop any money but drop alot of Fish Oil Jaggal Clam's and Shiny Fish Scales which also sold for quite a bit. I mad atleast 50-60 silver at the end of this test.
All in all I would recommend the Bogstrok Razorclaw's for the money and the reputation even though the fish are easier to find. The Feralfen Hunters I wouldn't kill unless they are closer by.
It was my first guide so plzz no flame O_o