The trick with doing this as a DH is really just trial and error at the proper corner. just gather like 6-10 rat callers and kite them to the corner, equip firewalkers and see if its doing damage to the callers. If it is, unequip, vault out and kite them around a bit then go back to the corner and try again. The only issue i have is when you get the neph. globe and it explodes, it messes up the positioning and if you're afk, all the callers just die.