Thanks to some nice advice from GAF I've been playing nightmare on my witch doctor (now level 36 with 750 or something dps on the meter), and getting to figure how to play wizard on the side. Now I'm hearing all this stuff from the horrible inferno difficulty and I'm wondering how my WD will play on there? I originally picked the class since it sounded like a class that can support others (maybe it was the doctor part) but I'm not really seeing it yet from the skill selection. Is there working supportive playstyle or will it be dire bats until the cows come home? I have no idea for example if the hex runed for heal actually heals others.
I'm slowly soldiering through Inferno with a Witch Doctor at the moment and I think the class is pretty viable on the difficulty, though the range of viable builds doesn't seem to be all that broad. I haven't really played any other class so my actual first-hand knowledge with which to compare is pretty much nil, but from this thread I don't get the impression that a limited number of builds being Inferno-viable is at all limited to the Witch Doctor.
One of the important things to keep in mind about Inferno is that there's a minimum DPS threshold you have to attain to really be able to function because of the time limits on the bosses and elite monsters, so any build that focuses primarily on survivability and sacrifices DPS to attain it is going to hit a nigh-insurmountable wall at the end of Act 1, if not earlier. I learned this firsthand and had to heavily re-configure my build as a result.
The need for DPS makes Vision Quest builds highly attractive, though getting by with Splinters seems pretty possible. The other primary attacks just don't seem to do enough damage to warrant their use. You could probably make do with one of them, but they'd be sub-optimal at best, I think.
Pets decline in usefulness as the difficulties go on, but as of Inferno they pretty much fall off a cliff. The Gargantuan still retains some utility as a distraction and a stunner, but any serious tank functionality he offers begins to dwindle dramatically. Zombie Dogs are a sick joke, frankly. I still use them because I'm mule-headed like that, but I highly recommend that you do not follow my example. Apparently some guy did some testing and discovered that pets benefit from raw armor and resistances, so I'm currently trawling the Auction House to get both of those up as high as I can to see if that improves their lot any. I sincerely doubt it'll make a meaningful difference, but I suppose it's worth a shot.
The non-percentage healing skills get to be pretty useless when you reach Inferno. Hedge Magic just doesn't heal anywhere near enough to cut the mustard come Inferno, and Haunt's healing capabilities are so paltry as to be meaningless. The only healing abilities you have that scale with gear are the Leeching Beasts rune for the Zombie Dogs and the Healing Journey rune for Spirit Walk. Leeching Beasts is useless because Zombie Dogs is useless, and Healing Journey is fantastic because Spirit Walk is the Witch Doctor's single most important skill on Inferno.
That's sort of the long and short of what I've gleaned from Witch Doctoring Inferno so far. It's pretty rough going at times, but the class seems to be able to handle it with at least some semblance of aplomb. I haven't really managed to put together a build I find really genuinely satisfactory, but I've been managing to make somewhat steady progress on the whole.