Star Trek: 10 Things You Didn't Know About Phasers

Hand phasers are typically seen firing one narrow, highly accurate beam, but they could be configured for many more firing patterns.

By adjusting the width and height of their spread, phasers could shoot wide beams or a cone-shaped phaser sweep. Wide beams (also called a full spread) could be used to quickly take out a whole room of opponents, like Tuvok did to incapacitate all of Voyager's bridge crew in the episode Cathexis. Phaser sweeps however were most effective when you needed to hit every single part of a room. Starfleet used phaser sweeps throughout DS9 in episodes like Homefront and The Adversary to locate Changeling infiltrators. As we mentioned earlier, these sweeps were set to a specific frequency that would cause any Changelings disguised in the room to revert to a liquid.

It's likely that these settings aren't typically used in large-scale firefights like The Siege of AR-558 simply because they consume way more power than a direct beam.