The Dervs in WC have a rare drop of decent jewels (jade, topaz, and carnelian so far for me), though I do not know at this time if the other derv areas have this rare drop.
i was camping the dervish camp 2 and my grouo member looted a topaz, thats the only time ive seen one but this means that the dessert dervish's have jewls too (please excuse my spelling i was in a hurry)
why can they run and cast? with channeling maxxed at 14 i can take 2 steps and turn around a little while casting that's it. anything else and boom it's interupted
The militia in West Commonlands may give you something for Derv rings, but they will not help you kill them, so zone, do not run for guards. Also, many of them backstab and like other NPCs they can cast while running. They generally stay in their camps, but when the camps fill up I have seen them spill out and wander around near the druid rings.