I did have a dragon fall on me, but not in the way you described...
I was fighting one, I was on a stone bridge in Morthal I think. The dragon decided to land on the bridge and sat right on me. The physics bugged out and it launched me off the bridge! If the physics were more realistic, the Dragonborn would have been killed by a dragon who just sat on him.
I was actually recording when it happened, maybe I can get a video posted here later?