My Build Above. Mostly from solo/duo play.
In nightmare I was doing a similar combo, using firebombs bouncing around. I was quickly taught a lesson in Hell. The main thing that is true in most cases, is to take it slow and remember where your cleared path is for kiting. It is better to clear a nice path than to try and sneak around only to end up kiting the entire zone to your spawn spot.
Soul Harvest, as annoying as it is to be up close and personal, is the key to WD. Zombie Dogs drop Health Globes more often than not and the Big Gargantuan is a really nice distraction. Don't be scared to lose your summons because they are always back in time.
Anyway, the point of the build is to use pets as distractions once your initial SH/Locust cast is up, my Swarm is ticking for ~783 per second, on every mob, that is nothing to sneeze at. Add in the little bit of dps from pets then you stand back and (Shift) click darts.
Big Bad Voodoo (BBV) is there for you in emergencies and rune adds another 30% to the already insane locust tick. Really nice for the 3-Named rare packs.
When in doubt, kite till your Gargantuan is up again taking stops to dart/locust if you have the mana.