Phase hunters in Netherstorm have quite the chance of dropping mote of mana.
Here is a map of them;
Phase Hunter - NPCs - World of Warcraft
Grab the quest- Recharging the Batteries outside of the Runs of Enkaat, then head to the edge of the ruins and hunt the Phase Hunters, they drop 1-2 motes, and you can use the quest device to burn them down fast from 1200 health or so- it gives you a warning message when to use it.
Even when you have 10 for the quest, you can keep using the device till you turn the quest in.
Edit: Kirin'Var Village might sometimes be faster to farm primal mana from, but it's usually very very camped. So this is just a tip to good primal mana farming if you're not online in the middle of the night or very early in the morning. :-)