Like Tailors, leatherworkers can craft leg armor enchantments you apply to your leg armor. As usual we expect power increasing items like this to be in demand and profitable!
Two types and two rarities
The formula is similar to tailors, with two types of armor, covering tank itemization and physical dps. For each archetype there are two rarities, a rare version and an epic version. The Epic versions are obviously the most in demand, but they do require Primal Nether, which is currently BoP. They were made tradeable in the 2.4 patch of TBC, which would coincide with Phase 4. As such you will still be stuck running heroics if you want to craft these in volume.
For physical DPS the patterns are the Cobrahide and Nethercobra Leg armors. The recipes come from honor Hold or Thrallmar, at Honored and Exalted respectively. They both require Heavy Knothide Leather, Cobra Scales and Primal Air. The Nethercobra requires significantly more of each, as well as a Primal nether.
On my realm you get about 250 gold profit on the nethercobra armor, if we valued our Nethers at zero gold. That increases the value of running a heroic by quite a bit! The Cobrahide armor also shows a decent profit at 38 gold.
The tanking version are the Clefthide and Nethercleft Leg armors. The recipes for these come from the Cenarion Expedition, once again coming through at Honored and Exalted respectively. The recipe materials are Heavy Knothide Leather, Thick Clefthoof Leather and Primal Earth, with a primal nether needed as well for the Epic quality Nethercleft leg armor.
Current prices on my realm put the profit at 290 gold for the Nethercleft leg armor and 45 gold for the Clefthide Leg Armor.
Obviously we expect the physical DPS armors to have significantly stronger demand, as there are generally a lot more DPS players than tanks. I would keep all variants in stock if you can, but definitely prioritize your nethers for the Nethercobra armor, as it likely has a much higher sale rate.
You can find my TSM setup below. It will post one of each for at least 20% more than crafting. You will have to set a value for primal nethers to make it work. To get there open /tsm crafting and navigate to reports and materials as shown in the screenshot. I’d suggest setting it to a hard coded gold value, whatever you prefer to value them at (I haven’t learned any Primal nether recipes, so it doesn’t show up for me).