https://www.bluegartr.com/threads/12...tions-requests
He does say that they turn it off to test at the end, however that is for fight balance rather than class balance, and there are some fights that they haven't tested in a true completely toolless state - he also hints that the dev team have "sort of cleared"
As another example of where they get their testing wrong, when Ninja was released and then nerfed shortly afterwards, Yoshi-P remarked that the community worked out a much better rotation than they expected.