I set up a relatively simple scene similar to your "Prey and Predator" example. I have tripple checked an everything should be working, but the predators simply do not attack. They occasionally wander close to the prey but never attack.
I've got them tagged as "Predator" and "Huntable" and have the settings in the individual objects as "Aggressive, Large, Predators" and "Prey, Medium". I've located them within very short distances of one another. I've set the dead object to the same "Dead Cube" that you use.
What else can I do to get the predators to attack the prey?