Oh, it is so easy to become over focused on measuring things. Metrics can be very valuable tools and provide valuable insights. Metrics can also be applied with great naivety leaving a wake of un-realistic and un-manageable expectations. I personally have two simple rules for metrics.
Tracking Trends is far better than absolutes
Measure success against a goal is better than counting work.
When you over focus on counting work (Tasks, Stories) you start to take away your strongest competitive edge. The power to evaluate success and impact. There is nothing worse then an agile team flawlessly burning down a backlog of stories that results in zero impact against a larger business goal. The team was productive, but the organization remains disappointed. Sadly this type of relationship leads to measuring more things to figure out why teams are broken.
“Teams work so much better when they are solving real problems”
Lets look at a simple scenario.
The problem: Reference-able customers are low on a new product.
I ask the team to fix these 15 support issues as quick as possible. If I were to do this, I know they would fix them efficiently. I also know that those issues would be replaced by 15 more; and so on.
I tell the team we have a problem with having a low number of reference-able customers and that we want need to increase that number. I probably would get those earlier issue resolved; I would also get other options for making the product more reference-able. In the end we may realize that those 15 issues, while important, are not a real needle mover.
So keep this in mind, you get what you measure. You measure tasks, you will get certainly get more tasks. But if you measure wins you will get more wins!