I made this Mote of Fire farming guide to help out players who want to farm motes instead of buying them from the Auction House.
Primal Fire comes from combining 10 Mote of Fire, so if you need Primal Fire, you have to farm Mote of Fire.
Mote of Fire
Incandescent Fel Sparks in Hellfire Peninsula at Throne of Kil'jaeden is the best source of Mote of Fire. The respawn rate is fast enough that you will never run out of them.
Watch out with the Felblood Initiate mobs, they are currently bugged and you can't kill them, they will always stay on 1 HP.
If your character's level is high enough to kill these mobs with 1 ability, then you can expect around 25-30 Mote of Fire every 10 minutes.