I’m with you - having a “breaker” that prevents updates beyond a certain number or percentage would be ideal. It’s available for preventing deletion of source accounts in ISC, but not for attribute changes or role syncs. That’s why tools like these have been created:
The attribute sync preview does not require that the sync be enabled, it just has to be mapped in the create profile. Run the script and it will show you which accounts will be updated. This is helpful when you make changes and want to be safe before turning on new configurations in prod.
However, what this still does not solve is the potential for source data issues (i.e., suddenly getting an empty job title on every record, or something similar) that get propagated to target systems. It’s just not a supported feature in the SP connectors.