Just to get it out of the way, I think trying to derive any person-specific data is a terrible idea. Variance in individual performance is overwhelmingly determined by variance in the work. It seems like my off-hand "assigned to Mary" got read as a much more significant statement than it was. My apologies for the lack of clarity. I think the virtue here is being able to analyze the system as a whole; micro-managing individuals against performance targets is obviously poison.

It would be excellent to see queue-based tools like cumulative flow diagrams and Little's Law modelers.