Well depends on whether yeh wanna aoe or do allot of dps to a single target.
I tend to lean more to aoeing when ever possible.

good spec, get demonic sacrifice sack an imp for 15% fire damage . get yer pali round up as many critters as yeh can handle park em. start the mage aoeing after the second consecrate after yeh parked the pali, have the warlock Hellfire. make sure yer able to retarget the priest to heal the warlock

For low lvl it might even be viable to take master conjuror for the firestone but once yeh get something half decent to fill that slot I'd get rid of it.

one of the things I've found is that its a whole lot easier to get shadow damage then fire damage making affliction/demo more appealing.

Just wait till yeh get Seed of Corruption thing just start dropping like flys :P