A common issue I see in action scenes (and in general) is a tendency toward group movement, wherein characters are all grouped together and move in synchronicity. They do the same things, are identified by the same adjectives and adverbs, and generally behave as a group rather than a set of individuals. Now, this isn’t always a problem. There are some instances where it can be an effective technique, but in action scenes it can drain your story of tension.
The mask-clad figures closed in, reaching for Sarah, Jane, and Smith. Smith and the others stumbled back. He shouted, but the figures didn't even slow. Their masked faces hid their expressions, but their eyes were cold and hard.
While this expedites the process of describing the action, it also takes away a lot of the character and the potential for tension, and the description and details which can really make an action scene. Because the attackers are written as a group, you can only be so specific about what actions they take. Unless all three attackers grab the wrists of all three defenders, which feels artificial, you can't delve into the details. Writing the scene this way steals its thunder.
Consider the scene written with more individual characters:
The mask-clad figures closed in, one reaching for Smith's hand. He shouted, stumbling back. One of them grabbed his wrist and he tried to yank himself free. The attacker squeezed hard enough to bruise, his eyes cold though his mask hid the subtleties of his expression.
You can be more detailed this way, and while we don't have the details of what Sarah and Jane are doing, if we're in Smith's POV, it's more likely that he'd be aware of what was happening to him and fuzzier on what was happening to the others.
However, group description isn't always a bad option, but like most things it needs to be employed at the right moment. For instance, if your POV character only has a few seconds to take in what's happening, and there's not a lot of movement or description involved.
Jane looked out the window, her eyes fixing on the mask-clad figures as they stood still and silent beneath the streetlight. She turned back into the room, already running.
In this instance the figures can constitute a group because there isn't anything to distinguish when, or time for Jane to notice any but the most obvious details.
Another reason for this kind of description is the desire to communicate everything that's going on, but action scenes are best when the reader can feel the fear or tension or excitement of the characters. The best way to accomplish that is to focus in on the details, on individual characters and their feelings and actions at the time.
It's all right if the reader doesn't know exactly what happened with Smith and Jane, if the POV character is Sarah. It's fine to sum things up with them, but you have to immerse the reader in what's happening with Sarah. For instance:
Sarah stalked up behind the masked figures. One of the men was demanding that Smith or Jane reveal her location, and Sarah used the shouting to cover the sound of her footfalls. Her heart pounded in her chest, so loud she felt sure the closest figure had to hear it. She tightened her grip on her gun, taking a deep steadying breath as she pressed it to back of the figure's neck.
"Not a word," she whispered, her lips all but pressed to the shell of his ear. The man stiffened, the tendons in his neck tight enough to string a violin, but he said nothing.
For most of this bit we have no idea what's happening with Jane and Smith, and we don't know exactly what's being said to them. Sarah's actions are what's important, as well as how she's performing them and how she feels about them. That's what draws the reader into the scene. Jane's and Smith's reactions and situation can be given a moment later, through Sarah's POV. For instance:
Sarah looked up and caught Smith's gaze. Smith looked back to the figure in front of him before he could give her away. Jane stood glaring at the masked leader, her eyes blazing as she spat at him, unaware of Sarah's rescue.
That's a bit stiff, but you get the point. When a group of characters move as one, you lose the opportunity to provide details. That’s not to say you should never use it, of course. Group movement can be wonderful way to communicate a lack of individuality among the characters. It can be used to create the sense of a group mind, or lack of individual will. I’ve also seen it used effectively in love scenes in which the details were meant to be glossed over and what was important was the emotion of the moment.
The important thing to remember is that it’s a trade off. Details, especially personal character-related ones, draw the reader in. So, if you’re going for tension, as with an action scene, specificity is often the best choice.