Actually, VoS might be very useful in many situations in PvE, not necessarily farming only.
I made lot of HM missions with H/H thanks to VoS. e.g. for me, the pain in the ass was Gate of Pain HM with H/H. Even with interrupters I kept on being wiped out by Terrorwebs or Torturewebs. And with VoS, you can solo them and save your party from unnecessary wpie outs.
Few sugestions:
If you're running VoS, you basically take 1/4 cast enchantments, just like Dan said. This is because you can safely cast 1 enchantment when VoS ends and then recast VoS and still having 98% chance of not getting hit by a spell. So your choice should be Mystic Regeneration, Mystic Vigor + maybe Faithful Intervention as a spike rescue. Add a stance like Conviction or Physical Resistance. Finally, get 3 attacks skills - 3 is a MUST for a dervish to have. I'd suggest Victorious Sweep + Mystic Sweep + Wild Blow/Zealous Sweep. If you want to have a VoS-removal, go with Irresistable Sweep. Nice attack, and might save your ass just in time.
Good try, keep up the good work mate