I've not had one make contact yet, but they've come so close, that in the one area where they were getting closest, I've stopped flying.
I think enclosed blades would help, the Phantom will self right and self balance if it's impacted, but not if the blades are slowed down or stopped by the impact, then it will get real challenging whether it would recover in time.
The scary thing for me is this was at the end summer beginning of Autumn here, and not even close to breeding or nesting season, so I hate to think what they'll be like come Spring.
I've wondered about some kind of audio transmitter on it, that would be loud, scary, or ultrasonic and scare them away, but it would need a lot more investigation than I'm happy to try to put into the system. But it could make them see it as even more of a threat and get even more aggressive with it.