If you have a work environment that only kills the marginal...then you have a work environment that kills the marginal. You need to start thinking about physical requirements and medical examinations before hiring, much like the military. Or maybe you need to think about putting a stop to a system that is really about hazing instead of getting stuff done.

The second might improve other things about the efficiency of your business as well. That will have economic consequences not just to you and your employees, and is therefore a thing of proper public scrutiny.