I had a boss that was extremely good to work for, but she didn't have management experience (given the nature of the organization, this would be expected), so she leaned on outsourced HR for advice. Not only did their advice lead to me leaving much less amicably than had been (mutually, I thought) planned, but they also opened themselves up to liability that wouldn't have been there otherwise.

The "bad cop" analogy is spot-on. I've used that exact analogy—my boss (unwittingly) played "good cop", while the HR consultants played "bad cop".