Fist off...this IS a Vision Quest build, so if you don't like to play that way, don't bother with this build! One thing I like to do though is save the spamming of the cooldown spells to nuke things, instead of just keeping the 300% mana regen active.
And here's the build:
First off, as you approach the boss/elite mob make sure you have a newly summoned Garg. Run up to them, and immediately pop Spirit Walk to get into the middle of them, then Soul Harvest > Big Bad Voodoo > Fetish Army > Dire Bat (Spam DB this untill everything dies, keeping SH and SW on cooldown).
+20% from PtV, +30% from BBV, +(however much it equals out to) from SH. Fetish Army gives us a %250 weapon damage AoE burst, and then we use up the remaining 18 seconds or so of BBV to spam Dire Bats with the +30% damage and 20% attack speed increase.
In my experience, it brings the elite mobs in Hell down to ~50% life, and then Dire Bats and your other team mates should have an easier time of mopping them up.
I have yet to test this out in Inferno, so I'll update when I get there.