Hell is about survival and endurance; as others have said you do not burst things down, so this build is about compensating for mistakes, survival and killing stuff. Like most of you, I've tried lots of different builds and this is what I settled on for surviability. Even with three dead people on a boss I can either kill or distract with the pet and rez people instead of a wipe.
Poison Dart (Spined) - Decent damage + mana recovery. Toads is a personal favorite but they are simply too difficult to direct damage. When they work, they hit very hard, they just don't hit all that often.
Fire Bats (Dire) - Main damage spell just like most other people. I also like grasp of the dead, but this seemed a lot less useful in hell due to all the teleporters.
Spirit Walk (Healing) - Damage, lag, mistakes, and stupid players happen. You need an escape. You can also pop this for a quick heal instead of a potion.
Soul Harvest (Sipon) - Massive damage boost plus another quick heal. If I didn't want the health, I'd go for mana. This is probably players choice.
Hex (Hedge Magic) - Useful CC and a bit of healing. Small cooldown so its great for topping yourself and the party off between encounters if needed.
Gargantuan (Wrathful) - Small cooldown and pretty much wrecks things and takes pressure off of the melee.
Vision Quest - another vision quest build. Return mana fast enough to spam dire bats.
Spiritual Attunement - All about the mana.
Spirit Vessel - this the oh crap skill. Mistakes happen and I hate dying. You can substitue something else here and the build is still viable.
Third slot options
Blood ritual - a good option. You have enough healing that is works too.
Gruesome Feast - cool, but unless you have great party synergy, health globes are too rare
Bad Medicine - a good choice, but since the main damage spell is firebats, not as effective. Coupled with Big Stinker this might be more viable, but I haven't needed it.
Jungle Fortitude - if you are undergeared, have latency or crappy reaction times, a good choice. Eventually you won't need it (at least in hell). We'll see about Inferno.
Pierce the veil - great spell, but hard to work in with the mana increase. You can't burst things down even with 20%, so I opted for survivability.
As you can see, the build is basically about juggling cooldowns. My combat rotation goes something like this, pop hex to get the fetish up, pop the gargantuan, run to the edge of a pack, pop soul harvest and then run back and start nuking. When mana is a problem, pop spirit walk (or save for an emergency) and return the mana to nuke more. After that it's mainly about using soul harvest, hex, gargantuan every time they are up and saving spirit walk for an emergency or mana return.
Like everyone else, I'm massively undergeared, but I'm still chugging along just fine in hell. Weapon is two hander (currently a mace I think) and I'm pushing around 6500 damage before Soul Harvest stacks. My health varies, but I try to keep at no lower than 17k (use gems). Things hit pretty hard and you take a lot of incidental damage while kiting. My preference is a 1H and offhand for better itemization, but the 2H are winning right now for raw damage output.
In order for this to work, you need decent kiting skills, decent situational awareness (stop standing in things that will kill you), and excellent cooldown management. I'll rehash something I said earlier...most builds are viable (even in hell), if you are having trouble its likely because you are massively undergeared. When I upgraded my weapon the last time it was a 2100 dps increase, just from picking up a 2H on the auction house. Visit the AH or farm the previous act for a day or two.
Good luck with whatever build you play and I'll try to answer any questions that don't involve figuring out how to turn on elective mode.