Let's leave aside the question of whether measuring everything is a good idea (maybe we'll come back to that one at a later date), and ask How do you measure the effectiveness of feedback on student work?
Comparing feedback to attainment is one way, but that would cause ethical problems, and since attainment is such a multifactorial event, how do you tease out the effect of feedback from all the other inputs?
"Accurate measurement of feedback effectiveness is difficult and perhaps impossible." Feedback: all that effort, but what is the effect? (2010) Assessment and Evaluation in Higher Education, 35(3): 277-289
The art of feedback then is in matching outputs to expectations so that no-one gets any nasty surprises late in the day. Measurement other than trivial recording of quantity and timing is spurious.