So I do a lot of work with the South African 7s team, sports science and analysis etc. We played the USA in Port Elizabeth and Dubai recently, and of course a lot of the pre-match discussion is to recognize what the opposition has to 'hurt you with'. Isles comes up a bit in those meetings, because he is clearly very dangerous, but he's not what I would call "dominant". Largely because one guy is easy to close down. All you have to do is maintain the line and close the space from outside, force him inside. And then speed is nullified, and the ability of the athlete to stop, step, change direction is far more important. So the team strategy is pretty straightforward, and we move on to the next aspects which are usually more complex. When you watch those clips, you'll see that most of his effectiveness comes from broken play - the ball is turned over and the defence is disorganized, and that's where the space is created.
But good teams are able to shut that down pretty easily. So when you watch highlights, you get a skewed view of how effective a really fast guy is. Also, they may be worth 5 or 7 points, but they can cost teams the same because often game nuance, defence etc is not at the same level. Not saying this is the case for Isles, but most teams will identify that the opposition winger is also their weakest defender. It's rare to be good in both directions.
That said, from broken play he's very dangerous. We in SA recognize how dangerous the USA can be if they find a few more guys like him. Right now, they're evolving, but the addition of 7s to the Olympic programme will stimulate the sport in the USA, and they have these great athletes. So we foresee a time when they'll be a real threat, not just because of incredibly fast runners.
So dominant, not really. Impressive for sure.