As of today's patch this is now sold from the barbarian beastlord spell vendor on the top floor of the PoK library (the same vendor who gives the parchament quest). Savagery is also sold there now.
Got mine from guild, forgot to ask where it drops, although I hardly use. Its just not mana efficient when I can pull with debuff and proc slow with epic. Only time I ever use is if theres too many mobs for shaman's to slow in time on raids. If its not memmed, I'll just slow with epic, switch targets and slow as many as I can.