Dwayne, your final comment is about as well-informed as it is helpful.
The data is not misleading, simply your assumption that it is solely because he switched from a 2-hander to a pair of weapons.
The switch was a switch of spec and gear to suit the different styles. And the sole, and non-disputable indication, is that he took less damage while dual wielding. That doesn't mean it is always the case, but it was the case here. Plain and simple.
You want to filter out the fact that he took softer hits? Edit the data set so it supports your assumption that dual wielding should represent more damage taken? THAT would be misleading, and bad science.