A good metric to measure how well a QA performs in an agile environment

Can you please help me think of 3 good metric to know if a QA team is performing well.

Here's the scenario:

Each of our testers are embedded on each product groups, each groups consist of a web developer and product manager all product groups are working autonomously for their projects and later submits metrics to measure how well they perform.

Since we are working in an agile environment which is everything is a group effort, I'm assuming that the metric of the product group reflects how the QA performs well and measuring bugs found in testing would not really give bearing for the group.

If you have inputs please help me. Thanks!