How do folks assess for employee burnout or overworking? What strategies do you use to identify and mitigate it?

Work-life balance questions are typically part of the Employee engagement survey - normally we include 3-4 questions, related with workload and employees' wellbeing. 
If you're noticing some challenges in this respect - you can use pulse survey including more question related with overall wellbeing, work-related stress, etc. 
One-to-one meetings between manager and employee ensure regular checks and feedback on the topic. 
Also there are companies providing resilience and mental health trainings that might use assessment tools for workplace stress and burnout.  

Beyond usual metrics of work allocation etc, we have built an excellent tool which captures employee pulse bi-monthly. Brief survey with 4-5 questions, pops up via chat bot, data is stored on cloud and insights are summarised. The HRBP's find the summary and dashboard to be useful and initiate proactive conversations with employees facing burnout, work life balance and other issues. 

We have just completed the tech onboarding of FlourishDx's Psychosocial Risk Assessment tool.
It is  is a leading workplace digital tool designed to address psychological risk and promote positive mental health and enhance engagement & experience. Here are some key features and benefits of this tool:

1. Identify Root Causes of Work-Related Stress: The tool helps to understand the root cause of work-related stress and identify burnout risk among other negative risk consequence factors. 

2. Meet WHS Legal Obligations: It assists organizations in meeting their Workplace Health and Safety (WHS) legal obligations - particularly psychosocial health and safety obs. 

3.  Attract and Retain Staff: By creating sustainable work practices that protect health, it helps attract and retain staff.

4. Customizable Assessments: The assessments can be customized to include the factors you want to assess.

5. Immediate Results: Results are available to admins immediately and update live once the minimum of eight responses have been received.

6. Time-Efficient: FlourishDx’s proprietary ‘work factors risk assessment’ can be completed in less than 10 minutes by most users.

7. Predictive Analysis: The tool uses algorithms to quickly and accurately identify hotspots of psychosocial risk across large, diverse operations and predicts the likelihood and consequence of harm at a group level based on various psychosocial hazards and their interaction.

This tool is part of FlourishDx's broader commitment to making psychological health and safety as important as physical health and safety in practice. It's a valuable resource for organizations looking to improve workplace mental health and productivity.

We use regular 1:1 check-ins with employees as well as company-wide surveys to gauge burnout and get a mix of of both qualitative and quantitative data. The surveys do a good job of providing an overall snapshot and showing trends overtime (as well as those relative to a specific department/project/manager). The check-ins provide more thoughtful, comprehensive data that more accurately assesses the specifics of what's going on - which can then used to develop strategic, targeted solutions to help mitigate. In some cases, implementing a more flexible work/meeting schedule has helped, but at other times solutions have been more complex and required updating or refining structures/systems in order for people to be able to work more efficiently and effectively. 
We also train managers on how to solicit/encourage feedback from their direct reports so they feel safe opening up when their workload does not feel sustainable - these situations only get worse when they're brushed aside or kept quiet.
Lastly, this probably goes without saying, but developing and emphasizing a healthy culture that recognizes and rewards people for their contributions, and helps them feel valued and seen, can go a long way toward lessening those feelings of burnout and overwhelm - even at times when the workload is significant. 
Let me know if it would be helpful to share any more of the specifics on how we structured questions, tactics, etc. 

we don't have anything formal