I work at a place that's very not diverse, and the groupthink can be suffocating. It's not so much as having sufficient nonwhites on your team, it's more about having people with different ways of solving problems. In my experience, a lot of mid-level problems get solved by inviting over a low-level programmer and have them look at the problem for a bit, asking questions about it.

Having a good distribution of perspectives is much more important than having a multi-ethnic hivemind.