I spend under 3m and got some gear and I managed to finish the game without any problems using this pet build - http://us.battle.net/d3/en/calculator/witch-doctor#WiUhYT!gaW!baaccY
I used Pierce the Veil instead of Spirit Vessel and Hedge Magic Hex for extra healing and some CC on really bad situations. Normally I would rotate it with Spirit Walk as a defensive CD.
I had around 900-950 resistances, 6000 armor (with enchantress), 22k DPS, 38k health, 1400 Life On Hit, 700 Life per second (this doesn't need to be high to keep pets alive).
Cydea wasn't a problem as locusts and kiting would finish the spiderlings and they were very slow. Azmodan was just the usual zigzag running and not much else. Haven't played for a long time but killed Diablo in one go. Pets would tank my clone and I'd kill it before the green stuff would kill the dogs and I would use Spirit Walk + Health Fountains to keep my dogs alive in P3 when he'd spam those flaming circles that kill your pets.
I do not think that pets need high Life per second since I've been running builds with as low as 500 and they do not seem to need more than 700 for anything in the game (unless 2k will keep them alive from Diablo's flame or the demon's flame breath in Act IV). Most of the time if I run into that rare instance that they do die (hammer guys also) then I just resummon.
With 1400 LoH I don't actually need them to tank since I'm also a tank doctor in essence. I started with around 900 LoH (700 from cheap weapon, 200 from ring) and since changed to an amulet with 600 LoH and a ring with 100 LoH.
So technically I can't die and neither do my pets so it's a win-win with 22k DPS. I can't afford the fancy stuff to get to 30k DPS (which is enough to melt Act IV mobs fast) but it's good enough as it is. I have a Mojo that I switch to to get 30k DPS if I see a gobo.
Anyway, great thread. Thanks for putting the info here. I never would have tried RoT if I didn't read this.