I would say it was dangerous due to the state of the road on the corner, rear wheel drive cars and farm mud don't go well together!
The overtake of you I don't see any issue with, although the difference in speed seems like more than 13mph so I suspect if we measured the white lines and worked out his speed accurately then he would be a little above the speed limit.
The overtake of the car in front was started before the warning signs for the corner and slow and if he knew the road then I guess he knew he could see far enough to stay safe, there does appear to be good visibility around the corner once he was part passed the other car and he could see far enough to start the pass as long as he was prepared to back off if necessary, he already had enough speed to get passed in a short time.
You went round the corner at 42mph, so he was allowed to do 43% more than you, even if he had stuck to the speed limit he would have been able to disappear fairly quickly.
If he had tried it in an average car then yes, I would think it was dangerous but it wasn't an average car and you shouldn't judge its capabilities by the capabilities of your own car. For me the biggest issue is that had the road been a bit wetter then that mud on the corner combined with rear wheel drive would have caught him out and his relatively heavy car could have caused some serious damage to other road users.
If you report it to the police then I doubt they would do anything, the only thing they could get him for would be speeding and that would take some effort to prove.
