All the answers here forget one thing: Fatigue.
As a martial artist (red belt in Shotokan Karate and Hapkido), I have the experience to know that if you aren't hit and disabled by an attack that you failed to anticipate, fatigue is going to get you.
If both sides are precognitive, there aren't going to be any mistakes. The fight is going to be pure exercise, with each combatant trying to score and prevent their opponent from scoring... and with precognition, neither side is going to score straight away.
However, as these combatants are fighting, they're going to be expending energy, running down their physical reserves... and sooner or later, someone's reserves are going to run out.
As a student of the marial arts, we did an exercise where one person would fight against a line of other people, ten seconds for each opponent until they had gone through the whole line, then the next person would take over fighting the line and the first person would go to the back of the line. With a long enough line, you're fighting for as much as several minutes.
During that time, if you're not the fittest person in the dojo, you're getting tired... and sooner or later, you're going to run into a situation where you're too fatigued to be able to counter the attacks coming at you, even though you can see how to counter them. At that point, precognition is not going to help you.
He who gets fatigued first, loses.
