As part of the Frozen Orb's animation, it spews ice in all directions, supposedly damaging enemies it touches. I wonder how exactly this works. Does it deal more damage if the orb hits the enemy directly? Does it deal more damage if more of the tiny shards hit the enemy? Can it hit the same enemy multiple times?
In one specific case, I've noticed that when enemies have the Missile Dampening affix, that Frozen Orbs last a very long time. They seem to travel for a set distance rather than for a fixed amount of time. The whole time they're moving, they still spew ice, but it's hard to tell if it's still damaging the enemies for its entire lifetime or if it's just an annoyingly long death for the spell.
Best Answer
Attempting to answer some of the questions simply through gameplay observation:
Does it deal more damage if the orb hits the enemy directly?
The majority of the damage seems to be coming from the orb, during flight and the final 'explosion' at the end. The shards will cause the chilled effect but doesn't seem to do much damage at all. Its possible to do almost no damage to an enemy if you cast the orb next to them and it misses them despite multiple shards hitting.
Does it deal more damage if more of the tiny shards hit the enemy?
Again, the damage is very negligible from the tiny shards. Direct contact with the orb or being in the area of explosion at the end does the most damage.
Can it hit the same enemy multiple times?
Yes, an enemy can be hit by multiple by the orb as it passes through. If they are near the end of the orb's path they will also take damage from the explosion at the end.
Troyen's bonus question:
how do the orb/shards interact with Life on Hit and Area Damage?
I can't answer for sure, but I'd imagine frozen orb has a hidden proc % (most likely to be a small value due to the spell's aoe nature) like all the other skills in the game. Each time the orb or a shard hits, you gain loh based on that proc % * your total loh. Ditto with area damage calculations. How each shard interacts with loh at this point is unknown.
Missile dampening interaction:
Because the majority of the damage requires the orb to pass through a target and the fact that missile dampening delays the end explosion as the orb seems to need to traverse a set path before exploding, it is advisable to avoid using this against bosses with missile dampening as the shards doesn't do much damage at all.