Well almost every strike of Alien is between 1 to 4.
Usually, as their dumb code want it, they attack alone and it happens that sometimes one jump with a week melee attack.
All you have to do is to focus on the single Alien, the others circling around are not a problem. They use one weak attack every... 10 seconds? when they are no more than 4 of course.
When they are more than 4, this is bullet time to reduce their number to 4 - 3 and then apply the thing again.
The problem I had with this method: It take a huge amount of time. Because of the speed of the rock paper scissors and the dumb alien code which seems to hesitate a lot before an attack