Average compounded time-taken for Statistics Workbench

I know what you mean and I'm afraid I'm not sure how to do this with the statistics workbench. Although using the old stats module you could pull out the time taken for each request into a csv.

I'm more interested with why you would want a statistic like this if you are doing a load test. Surely the point is to get an idea of the response time under given conditions. Not to start aggregating things over the course of the whole test?