That technique does look impressive…when you have a 250 pound guy slam into a 135 pound guy who stands there and takes it (interesting defense)!
Many years ago, my sensei was asked by the newbie of the day (they always ask funny questions), "Is Aikido powerful enough to stop a train?"
My sensei responded with, "Stop a train from hitting you? Yes, it's called tenkan."
But you are confusing sport with self-defense. I strongly suggest that in real life you do not stand there and put your fists up (ala boxer style) and wait for his next strike!
And if your assailant out weighs you by a 100 pounds, you have to seriously assess his intent. Is this a scrap at the local bar, or are you in a back alley? Real danger is going to warrant something more serious. You either run (chances are you'll outrun this guy) or make vital area strikes (to the knee unfortunately) with a guy that size; he won't feel many other atemi.
Sport and self-defense are two different things. What kind of defense are you looking for: One for the MMA sport (which disallows anything effective against jumbo opponents), or one for self-defense (where your objective is to live)?