Ok, so what you do it go to Shadowmoon Valley and enter the Deathforge and take the first entrance. Make your way about halfway across the bridge and jump off the right just so you can see the warlock ritual. The Infernal Soul inbetween them all instantly respawns after you kill it, and drops tons of motes of shadow and other various greens. I farmed for about 2 hours and got 15 primal shadows and 8 greens. Happy farming!
Coords are 38,39
