Can you provide some more context, in particular how your entities look like and how you validate them manually? Are the approaches comparable? Hibernate Validator might have to to more work doing validation as per Bean Validation compared to a hand-rolled specific solution.

Hibernate should be able to naively handle this magnitude of field-level validations without resorting to manual validation at a class-level.

It handles the validation, right? As far as I understand the result is correct. The intend of Bean Validation is not necessarily bulk validation as you are trying to attempt. I am all up for performance improvements, but we first have to a establish a baseline.