Stack ranking will tell you when something isn't working, but the solution isn't always to fire, but rather use that data to fix things in a more general solution.

I found that team composition and role assignment matters a lot, at least if you hire people who are at least above a certain bar. Match a brilliant non-assertive coder with someone who is outgoing and good at getting along and at least decent coder, and the results from the two outperform generally either of them individually.

You can bring out the best of your employees or you can set them up against each other. This either brings everyone up or brings everyone down.

Wholeheartedly agree with you on team composition mattering a ton, but how often do you have such an abundance of engineers and tasks that you can match them up the right way?