Docile with humans doesn't mean docile with predators. I have four roosters. My blue Orp rooster and my Delaware rooster are both very calm, even-tempered boys, but they are fierce at protecting their women. My Del, Isaac, loves to have his chest scratched, but he's large and strong enough, as well as very motivated, to protect his girls to the best of his ability, which I'd say was considerable. That doesn't mean he'll live through it, but I'm sure he'll give a predator a run for its money. My blue Orp is huge, over 12 lb. He is not as maneuverable, but he has bulk and is super alert. I'd drop dead from shock if either of those showed me any aggression. They're good boys and I'm very pleased with them.
I have two BRs, one of whom is crippled so out of the picture except as a pet. The other one is very large, strong and a fabulous protector. He is docile and easy going except when I have to separate him from his hens for a period (long story). Then, he tends to bite out of frustration, but most of the time, he's really good. He's had brothers, owned by other people, who turned aggressive, but overall, I like BR roosters for my flock. I did have one aggressive Ameraucana a couple years ago, but I have one Blue Wheaten Ameraucana cockerel who is six weeks old that I plan to let run with the main flock, along with the BR, Dutch.
All that said, it's usually more of an individual thing than a breed thing.
ETA: A rooster's job is to buy the hens time to get to safety, not to really disable a predator, though some do manage, depending on the predator. That's what I have mine for, a first line of defense. I realize, as everyone should, that he will most likely lose his life in a showdown, but he has a noble job.
