I have known some big, strong, solidly built guys who couldn't take a punch...
And some skinny guys who are real scrappers...
I think toughness should be an individual trait, not one based on class or race...
Just as it is not based on sex.
Maybe that drow with the toughness feat is the toughest drow out there.
Maybe he can take a hit just as well as anyone else.
And yeah...Warforged get CON enhancements, why not toughness?
That always made little sense to me.