Understanding where critical tasks are at play in resource overloading is also, well, critical. For example, Jack may have several tasks to be completed in one week (showing overload in a standard reporting function), but they may be non-critical tasks. Moving one task after the other probably won’t delay either project, so there is no need to cut scope or get more resources to avoid a delay.  On the other hand, it may be the case that Sue is assigned overlapping critical tasks, which indicates an almost certain delay in one project or the other, or both.
In this scenario, it's critical for the team to take action and resolve overloading on Sue's critical tasks. Jack's overloading it not a priority.