Ok, so there has been some speculation on how Creepers works. I finally got a chance to try out the skill today, and it was way different than what I was expecting.
At first, it looks like regular zombie wall, but soon after, a zombie crawler will spawn followed by another and yet another.
They persist for about 4 seconds after the wall is cast, with each one dying out in the order that it appeared.
They do not follow the Witch Doctor.
I imagine this would pair well with Lob Blob Bomb, and corpse spiders, as these skills all work similarly.