Here is a great Witch Doctor build (build is at around level 30)
Skill setup:
Poison dart + Mana rune
Flaming skull + Jumps up to 8 times
Locust swarm + double-jump rune
Wall of Zombies - Lock out that horde of enemies and watch them melt due to your locusts
Gargantuan - Big boy picks up the slack and gives you more survivability
Intelligence buff Aoe + Mana steal (you really need a lot of mana as WD)
Passives:
Mana/Life regen upon health globes
+20% damage, +30% mana cost.
