I think you can keep from this method (the HEART framework) some metrics that can be applied to an employee:
Happiness;
Task efficiency;
In my opinion, in this case, better results can be obtained if the employee is required to use at least two similar tools (maybe the old tool used and the new one). In this case, you can measure engagement, adoption and retention.
In Measuring the User Experience on a Large Scale: User-Centered Metrics for Web Applications, by Kerry Rodden, Hilary Hutchinson, and Xin Fu from Google, you can see you can use this framework for an enterprise, with some observation.
For example, Engagement may not be meaningful in an enterprise context, if users are expected to use the product as part of their work. In this case, a team may choose to focus more on Happiness or Task Success. But it may still be meaningful to consider Engagement at a feature level, rather than the overall product level.