Rather than "timing" the steps, my company counts the number of lines picked in a time period / shift. I guess it really depends on what the goal is of your metrics, but in our case we wanted to gage what was reasonable / possible as daily work item throughput. It also helps create friendly competition and urgency among the team (while keeping it fair). Our orders have a wide range when it comes to the number of lines picked / packed, so measuring that number of lines at the picker level helps incent them to find efficiencies, or not "cherry pick" the easy 1 and 2 line item orders. Picking a larger order with 20 or 30 line items helps boost their personal numbers.
Anyways, just some insight in case it helps. The time stamps on System Notes would certainly give you much more granularity to work with. Best of luck!