Your hounds and spiders do damage based on your current DPS, which is influenced by your intelligence. Soul Harvest will increase all of your damage output as a Witch Doctor, from all of your spells.
It really wouldn't be very good otherwise.
So far I've used two builds with a decent amount of success soloing Inferno Acts 1 and 2 (just grinding for gear and killing champion packs and the end boss). Honestly, the best and most powerful thing you can do in Inferno is just gear yourself up. I've heard of a lot of random builds working, as long as you gear yourself in a specific way and have a pretty decent weapon. Also, using the Templar pet while soloing is a good idea, since he will actually tank for you.
As far as a specific build for soloing champions in inferno, I've had pretty good luck with a poison dart build. For this to be successful you'll need to stack a little bit of attack speed and have a pretty decent weapon though. You'll also need to prioritize abilities that'll let you kite. I like the DoTs because they also help with large packs and you don't just get melted, but you can probably change out some of that stuff for your own personal preferences for your own play style.
I like the ZomBears build, but I do agree that it is difficult to solo with because you've got to be fairly close for it to work. I've been playing around with build alternatives and so far I've only come up with the Poison Dart build.
Editing this in since I just tried a new variant of poison dart build that I liked more. This build for darts was much more effective due to the amount of CC you gain from Horrify and Hex. I had a much easier time doing solo Inferno Butcher runs with this build that my previously mentioned one.
Link to ZomBear build I used for a while that also worked well.
This Pet Build has also been said to be pretty effective, but I've not tested it much myself. It looks interesting though, and a couple of people on Blizzard's Witch Doctor forums have said it is good.
Best Answer
I did some digging regarding this situation and it seems that there was a bug not that long ago in the console version regarding Set bonuses, here's a video that shows the bug:
Video
This video shows how you get a 100 Vit bonus by wearing two pieces of a set, you logout and login and you get another 100 Vit increase due to the Set bonus, and even if you unequip the items, you still keep the bonuses in your base stats.
According to the console hotfix log from Blizzard, this bug was fixed in September of last year and it mentions that it just fixed the new ocurrences but did not fix the affected characters. All affected characters were set to the right statuses by the 1.0.2 Patch release 10/01/2013, these are the patch notes.
This is the closest thing I found or I could think of that could have affected your Witch Doctor, as it seems consistent enough, but given the timeframe, the only way this could still happen to you is if you hadn't added that patch and kept playing offline (which I've no idea if it's possible in the console version).