Here's an easy gold-making tip for disenchanters out there:
When your faction takes Halaa, visit the weapon vendor there and buy the (3) limited quantity Avenging Blades from him. They cost a little over 2g and DE into Greater Planar Essence (worth 6g on my server). Sometimes you get 2, and I even got a Large Prismatic Shard once! Don't bother with the other limited quantity items, they're not a profitable DE.