Burnout isn’t only/exclusively driven by workload, but rather unmanageable workload.
The amount of workload is an issue, but also having to get a certain workload done in a certain time is an issue. What do you do if you don’t have enough time to put the slide deck together? Or if you are asked to do something you never did before and don’t have access to training so you can develop that specific skill you are lacking?
Unmanageable workload is also when your manager goes back on a principle decision once taken. You can’t keep going back to square one and start over again and again. If decision making is completely out of your hands, you can consider this also as unmanageable workload as you don’t have a say how to do your work. If you are not managing it, it’s unmanageable.
If work is unmanageable over a long period of time you burn out.
Making sure you can manage the workload is your manager’s job. If he or she gives you too much work or not enough time to complete it or not clear enough guidance than it is your job to speak up.