I cast shadow power and shuriken cloud right after to snapshot the life steal. Then I run around bumping into enemies (you see their health bars pop up). Each bump nets me a life steal tick of around 2-3k. When I have 20-25 monsters following me, I cast shadow power, caltrops and mfd and rapid fire away and clear the screen.
It's not ground breaking and it certainly does not match up to the power of pestilence, but it saves a bit of time not having to cast shadow power and start channeling for only 5 enemies. It works wonders in fields of misery and scavenger's den.