At the moment I've been farming Vanguard pieces for my DK, as well as Masterwork pieces for my Hunter. So far I acquired Vanguard Vambraces, Vanguard Gauntlets & Vanguard Girdle. Absolutely no luck with Masterwork, although I've been keeping my eye on the AH as well as farming Molten Core by killing the Flamewaker Priest standing next to Salfurion Halbringer.
BTW, if anyone wants to sell me any Vanguard/Masterwork pieces that would be great. :)