This is how we play:
If Voldemort is out and there are other villains, he does block Confundus. He is clearly labeled as a villain, so the requirements can't be met.
However, once Voldemort is the last man standing, Confundus ALWAYS works. So it evens things out a bit.
Thanks. That's how I played it but wondered if there were any special rulings I didn't know about.