In order to help this drill become more effective, with respect to realism, try these simply modifications:
1- attacker does not step back before attacking, they should attack from a natural standing position, like a pararrel stance, without 1st moving away from the target
2- attacks should be limited to 1
3- the attack should not be pre-arranged
4- the attacker must try their best to strike the defender
5- counter attacks should be limited to 1, remember a true opponent will not attack using a single technique, nor will they stand still & pose or cooperate with the defender
6- the distance is determined by the attacker, according to the techniques used for attacking, for example, knee to groin, close quarters, side kick, further apart, flying kick, even further apart, not that too many flying kicks happen in the street, but attackers do come running at you
7- the counterattack should be approriate for the vital spot attacked