As a side note: Weapons.
Yes, there are 1h + OH witch doctor items.
No, you don't want them.
You want a big, slow 2h with fucktons of +dmg on it. If it has a socket, get the biggest ruby you can find and stick it in. Ideally about midway through Nightmare you should have 1200+ damage as a base.
As for passives, I personally prefer: 20% damage reduction, 10% mana + 10% int health bubbles, 15% mana cost to health + 1% health return.