I am currently in Hell mode act III. (Solo)

This is what I use to solo in Hell at the moment. Be sure to grab the Follower, most people forget. I use Templar with heals.

http://us.battle.net/d3/en/calculator/witch-doctor#aUdk.T!WVZ!acZZ.c
I sit at near 7k damage unbuffed and 21k HP.

Skill 3 is up to you. Hex/Mass Confusion/Big Bad Voodoo are the preferred choices depending on the situation.
Gargantuan can be switched to Restless Giant if preferred.
Change Jungle Fortitude to something else, if you prefer.

When fighting Plague mobs, try to run away and switch to flaming darts.
When fighting a Yellow mob, clear the trash first if possible and switching to Snake to the Face can stun them for 80% of the time with Bruiser Giant.
Vortex/Teleport are your worst enemies.
Dodge the ice bombs, move away from arcane sentries, these are all common sense.
If you can't kill something, just ignore them and move on.

Don't just stand still and fight.... There are a lot of narrow spots where you can cut off mobs with wall and start DPSing them down. The zombie wall itself does massive damage. I find that stairs are the best place to lure mobs if you can.
If getting low, spirit walk and run away until the CD is back up.

This is what " I " use, and am so far successful with. The build itself is only as good as it's user.