Turnover is tough. It is a problem for a few reasons. First, it hinders the ability to get work done. Second, it signals to the remaining employees that there are issues. Third, its a huge emotional strain.
First, let's answer your question about "is there a meaningful way to create a cost benefit for the three mitigation techniques listed?" Yes, simply identify the cost of each employee leaving. The industry accepted practice is to multiply the salary of the person that left by 1.5 to 3, depending on the complexity of their role. An example of this is: John's salary is $30,000. The cost of attrition for John is $30,000 X 1.5. That would be $45,000. You would do this for all the positions that have left. Then determine the cost of the three mitigation techniques.
- Documentation of tasks - probably about $25 - 40/hour of documenting tasks,
- Cross-training employees - at a minimum it will be the hourly cost of the employee training AND the the employee being trained. If there is training material to develop, then that would add to the cost of the training
- Hiring bench strength, you would have to calculate the budget impact of that. That would be a combination of the employee cost (salary, benefits, etc.) and the cost to train them.
If the cost of the mitigation techniques are less then cost of employees lost, that's a benefit. But that is purely an accounting determination. The problem you are facing is probably a symptom of a larger organizational issue. My suggestion would be to get at the heart of that first. This can be done with interviews and surveys. Involving the remaining employees in solving the issues that are uncovered through the "detective" work is a GREAT way to start to stem the tide of attrition. They feel part of the solution, which they are.
Happy to share how to do this in a short call. Thanks!