Someone who spoke to Don Vu during the Reaper of Souls launch party noted that Frozen Orb was not working as intended. The orb is currently doing double the amount of damage it is supposed to be doing compared to the other arcane orb runes.
It seems that the orb isn’t doing it’s initial half damage, and then doing the other half of its damage upon impact; it is probably doing full damage as it passes through stuff, and then another full damage on impact. Which is probably why frozen orb wizards with enough cold damage and arcane orb modifiers, are shredding through higher difficulties with what is subpar sheet damage.
I use frozen orb myself, but have purposely left out a lot of these from my main character since I notice a significant difference in the kind of damage it does compared to my loot 2.0 one which does have increased arcane orb damage on the boots. Until it is fixed, I want to see if it is going to be worthwhile to continue using the skill.