What you seen is probably the Fire at Will power. I run two copies of that power on my Souvereign, you may have noticed it. Randomly targets everything in range with rapid beam shots.
That is a power for tank though, as it draws a lot of aggro.
As a tac you are better of using Beam overload, which fires a single very high powered beam at a single target. Capable of dropping a shield at once, if you are not up against a battle cruiser or a dreadnaught at least.
And then, something i used to do in my cruiser (notso much these days dor soem reason) when I have enemies in my front and in my rear, I toggle targets and fire at 2 targets simultaneously as well....
Both Fire a Will and Beam Overload, as firing 7 or 8 beams at once for that matter, will drain your weapon energy significantly, esspecially BO, which means your DPS on each shot after that is lower, so give it a second to get back to full.