Ive never really been able to find out the truth on how the orb damage works. The damage on orb is quite low compared to other spells. Does each bolt dish out that much damage? or just a bunch of bolts...or possibly if all of the bolts hit the same target.... which is immpossible.
Each shard of ice that comes out of the spinning ice globe does its listed damage (before you counter in cold mastery) A head on orb should hit around 16 times, so in that case it would do more damage than most other spells, the probelm with this is that its pretty easy to avoid ALL of the shards. The good thing about it is that its damage is fine, its easy to use, and it has a big spray