I've tried farming a few different places at my current lvl (lvl 44).
So far it seems like the Vilebranch Troll mobs in the Hinterlands are by far the best farm mob I've found. They range from lvl 42 to lvl 50 and there are several elite types. http://www.thottbot.com/?s=vilebranch
-It's used for Wildvine Potions 'Restores 1 to 1000 health and 1 to 1000 mana -Used by engineers -Used by tailor -Used by leatherworks -Required to complete the Leatherworking Wild Leather work quest (two of them).
The AH fee is only like 30c - so there's very little risk and a stack of 20 wildvines can sell for 5g easily.
From the trolls you also get -Troll Necklaces: A repeatable quest that gives you 390xp @ lvl 44 for ever 5 of them you turn in (ALLIANCE) -Mageweave -Silk -Silver -Flask of Mojo (used for 4 different recipes and an item for a couple of quests: http://www.thottbot.com/?i=3159)
So you've got several money making drops with the Wildvine possibly netting you 5g an hour alone. And if you are part of the Alliance - the NPC right at the Aerie Park entrace give you around 390 xp for every 5 troll necklaces you turn in.
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