In my experience using Jacob's Ladder i found it hard at first to get multiple enemies, but I managed to get 3 in one shot. Having played a DM brute up to 40 the cone feels smaller to me than Shadow Maul.
Jacob's Ladder seems more like a line than a cone really.
One reason people might be having trouble hitting multiple targets is those damn snakes! They're bigger than most other mobs, and they move fast. I was having trouble lining up good shots on the snakes, but against the infected i could almost always get at least 2