What changes to specific Witch Doctor skills can I make through equipment?

Question

Before the game was released, data miners were speculating that each class would have a list of certain modifiers available on equipment that would provide small changes to the way class skills would work (e.g. "reduce cool down of wall of zombies by 2 seconds").

Have the existence of these modifiers on items been confirmed, and is there a list of what ability modifiers are available for Witch Doctor skills?

Are there restrictions on what types of equipment they may appear on?

Answer 1

As per DiabloFans' list from the Bradygames Strategy guide:

Firebats - Reduced Mana Cost

Haunt - Boosted Damage

Poison Darts - Boosted Damage

Spirit Barrage - Boosted Damage

Plague of Toads - Boosted Damage

Corpsespiders -??? (Transcribed improperly)

Locust Swarm - +% crit chance

Firebomb - Reduced Mana Cost

Zombie Charger - Reduced Mana Cost

Wall of Zombies - Reduced Cooldown Time

Acid Cloud - +% crit chance

Summon Zombie Dogs - Reduced Cooldown Time.

Exact magnitude varies with level and the exact item. Most of these show up on Voodoomasks / Dolls / Ceremonial knives, but they can appear on regular helms, offhands, and weapons as well.

Answer 2

You can actually get a look at this by searching in the Auction House, as each skill modifier shows up as an individual search. Here's what I was able to find, along with the visible ranges for each effect (it's very likely that these aren't the caps, just that higher ones aren't posted):

One handed and two handed weapons:

• Reduces resource cost of Firebomb by X mana. (AH shows a range between 1 and 7.)
• Increases Haunt damage by X%. (AH shows a range between 5 and 9%.)
• Increases Plague of Toads damage by X%. (AH shows a range between 5 and 11%.)

Off-hands and two handed weapons:

• Increases Poison Dart damage by X%. (AH shows a range between 5 and 11%.)
• Increases Spirit Barrage damage by X%. (AH shows a range between 5 and 10%.)
• Reduces cooldown of Wall of Zombies by X seconds. (AH shows a range between 1 and 3.)
• Reduces resource cost of Zombie Charger by X mana. (AH shows a range between 3 and 9.)

Armor:

• Increases Critical Hit Chance of Acid Cloud by X%. (AH shows a range between 1 and 6%.)
• Reduces resource cost of Firebats by X mana. (AH shows a range between 1 and 9.)
• Reduces cooldown of Zombie Dogs by X seconds. (AH shows a range between 1 and 6.)