Blocking everything with one hand/finger

Think about this for a minute. It doesn't matter how much faster the defender is than the attacker, because their finger still can't be in more than one place at once. Say the alien throws a punch at Beerus, then Beerus blocks it with his finger. The alien then throws another punch with another hand, aiming for a different part of Beerus' body. He can't move his finger to block the second punch without letting the first punch continue. And this alien even had 4 arms! Another thing is that if your punch gets blocked by a hand or finger, why not grab the hand/finger to hold it in place and then throw a punch with your other arm? I'm not suggesting this would work against a massively stronger and faster opponent, but we never see characters even try this.
Fighters mutually fooling each other with afterimages
https://www.youtube.com/watch?v=eehv-7lVK_g (all throughout this video but especially visible from 1:02 - 1:20)
Ignoring for a moment the scientific implausibility of leaving a hologram-like image of yourself just by moving fast, think about the mechanics here. To leave an afterimage that your opponent hits, and then get completely behind them without them even noticing, you would have to be significantly faster than they are (or at least faster than they can track). But if you have two fighters that are presented as roughly equal doing this to each other repeatedly, how is that possible? Is Cell somehow way faster than Goku one second, but Goku is way faster than Cell the next? Fighters that are close enough in speed to keep up with each other should never be able to fool each other with this kind of move.
Also, as TVTropes points out, if you were fast enough to completely evade an opponent's vision and get behind them without them noticing, it would logically take less time and effort to just turn around and attack them before they could hit you.
These are just two examples, there are many more.
