http://www.youtube.com/watch?v=t3uSTZXVhLo
Or, if you don't want to / can't watch the video, here's a picture.
purple is your start point, follow the teal line until you hit the left platform.
Red = Guardians, Brown = Kulle, they will follow their own teal path until they get to the right platform
Then, just use Bola Shot (with the Acid rune)
I only tested this as a DH, I'm sure it would work with other classes as well.