Most folks have limited range time and/or ammo to practice for self defense with a handgun. I think most of that time should be spent mastering the documented threat potential within 7 yards. Extending that to 15 yards doubles the distance, and covers well over 99% of all self defense shootings that actually have happened.
Spending time/ammo training at 100 yards for self defense is far, far beyond the envelope of reported events. Could it happen? Yes. How likely is it, compared to 1-2-3 or more outlaws at 7 yards? Way to the right of the decimal point.
Is it fun? Oh yeah.
Is it a realistic scenario? We can all imagine some scenario where it could happen - but we should worry about the real, not the imaginary threats.
As to defending yourself in court after such a shooting, I shudder to think what the prosicutor will bring out to show you were not at risk. How do you know the shooter was shooting at you, and not at some threat/target/game annimal between you that you could not see? Why did you not move to cover? How did you identify this person as the shooter? Could it have been some other person, not seen by you?
Now, it is possible that you will be out in level grasslands or desert, and the shooter will stand up so you can clearly see him/her shooting at you. But is it probable?
Not nearly as probable as the 7 yard threats.
As I said before, if you do it for fun, that's great.