By "Orb of Acid" it means a very large, very rapidly expanding wave of acid. If you dont have a way to teleport or keep yourself away from it, or it is activated remotely, it WILL kill you. Casting it off a cliff usually is not enough.
If you can use it, very good way to strip an area or break through levels. Additionally, 2 casts can easily deal with the consequence breaking through levels usually incurs.