Primal Mana

....................TRANSMUTES....................
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.....Mana<->Fire <-Air...............................
.....................|.......^.................................
....................v........|.................................
.....Life <-> Earth -> Water <-> Shadow......
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Best Way for Farm Primal Mana is Karazan. You get a bit over 9 Primal Mana per run. By far the best way.

The Way:

1.Clear up to curator. Pull the trash before the curator and kill them without pulling boss (mana wyrms and elemental only, not the constructs)

2. Pass by curator and pull all wyrms and elementals in next room , go up the stairs until the first level where there are a few more and kill everything there.

Tips: Wyrms are immune to magic spells so either get a staff/dagger if u are a mage or bring another class.
You can not enter from side entrance anymore it seems so you will have to clear the normal way.

If you dont kill Curator the trash should respawn in about 30min - 1hour if u stay outside instance. Best to bring multiple characters though making things much faster.

Most up to date comment and by far the best method to farm these :)

best mobs to farm these (and spot) is

http://www.wowhead.com/?npc=18866
http://www.wowhead.com/?npc=18867

the trick is to kill them fast (under 10sec seems to be about right)

if you dont the mageslayers will use spellreflect and the mana seeker will use mana burn

if you kill them fast enough as a caster they wont do anything! (they have about 5200hp each)

one hour = 7-10 motes for me (i need 6sec for one mob 0/21/40 wl)