What is an employers responsibility with respect to job decriptions updates

2 years ago specific tasks are moved from a Sr. Managers department to a lower level manager's department. The tasks requires the addition of a Full Time Empoyee, hired by the lower level manager who is now responsible for overseeing the tasks and additional employee. 2 years later, the lower level manager's job description remains the same and employee count increased by one.7 direct reports total. The Sr. Managers department is outsourced and is downsized from 30 employees to 15.