Still on Act 1 Hell.
I ditched Soul Harvest because not getting hit is better, the Int increase is situational, and I sorely missed having locusts. Honestly the only reason I tried out Soul Harvest for awhile is because every single build seemed to have it.
I just now got Healing Journey for Spirit Walk, but I haven't gotten to try it out yet (I've been using Jaunt which has worked pretty well for keeping me alive). I plan on getting Life to Hit the next time I find a great weapon that has a socket since I'm hearing glowing testimonies about it.
Also, how is Fireball (Flash Fire) in Inferno? I use it against large packs of enemies as an alternative to Spined Poison Darts (I don't have Zombie Bears yet, not a fan of a lot of the other costly AoE spells).
Pets are seriously that bad (when dogs are dying on Normal Mode, a mode where pretty much everything is invincible and it takes just Nightmare Act 1 for Gargantuan to start taking serious damage, something is wrong). You'll need to wait for the update which gives pets Vit scaling before they'll be worth trying out.
WD is also more about methodical methods of playing (which can be very active even if you're waiting for mana to recover) than the other classes.
Here is the build I used through most of Hell.
http://us.battle.net/d3/en/calculator/witch-doctor#acUdfR!!aaZZca
I was having a lot of mana problems early on, but this was resolved mostly by zombie bears. Both splinters and hex are pretty interchangable. I was often switching my last skill for different things depending on whether I was going solo or with friends.
For the first half of hell I used mana-less frogs, which worked pretty well. But in Act3 they weren't as reliable for consistent damage so I switched to splinters. The hex I was always switching, trying different things. Horrify with the mana rune was one of the better ones. Fetishes and VooDoo I felt were never worth it due to long cool-downs.
My playstyle was one of two things at all times. Kite using frogs/splinters, and spamming dire bats while lining up enemies. (dire bats goes THROUGH enemies and deals great damage, I'm still using them in inferno) I'm usually around half mana if I'm running around kiting. SO I often will spirit walk (mana rune) and get to near-full mana, and position myself to spam zombie bears. They DESTROY EVERYTHING. Best WD spell imo. They roll through elites, bosses, etc. Use them, but only do so when you can position yourself and you have plenty of mana.
I usually spend my entire pool of mana on bears, then return to kiting until I can spirit walk to full mana again. Remember too that you can grab health globes while in spirit walk. Between globes and healing rune on SH, you can get healed pretty quickly.
Like other classes, its mostly about timing and positioning. Spirit walk and SH are your best friends. If you don't have zombie bears yet, try another AOE spell that you can quickly spam. (no cooldown)