Actually, go look for the 'tokenadult comments on work-sample tests to learn that this approach has been known for something like half a century to outperform interviews.
This answer could possible address the test question. It leaves the other two issues I raised unanswered. Not that you have to address them, but just saying that the approach you guys implemented might work well for a very small subset of companies that share traits in terms of company size, structure and industry sector.