What are your qualms with time per element? I liked it as a metric because it kept the total deviation of results to less than 32 across the entire result set.

Using something like the overall run length would have such large variations making only the shape of the graph particularly useful (to me) less so much the values themselves.

If I was showing a chart like this to "leadership" I'd show with the overall run length. As I'd care more about them realizing the "real world" impact rather than the per unit impact. But this is written for engineers, so I'd expect it to also be focused on per unit impacts for a blog like this.

However, having said all that, I'd love to hear what your reservations are using it as a metric.