Not sure if this have been posted before, didnt find anything about it.
When you go out of shattrath, go directly south until you are in the bone wastes.
from there, go east and find the infested-root walkers, they usally drop 1 or 2 motes of life almost every kill. The root walkers are also everywhere on the edge of bone wastes where there is trees.
on my server, the primal life go for 10g, so it can be a quick 10g. If they go for higher than that on your server then this is for you. :P :wave:
P.S: sorry for bad english