Why would the targeting laser have to use that much energy? It's not doing any damage.
Really, the way to balance it is to control WHAT jumps out of subspace and how many of them. You can also set how long it takes for things to show up once you tagged them. Keep in mind also that its not incredibly easy to target ships. The targeting laser works like scanning in that you have to be pointing almost directly at a specific point on the ship, or no lock. You also have to keep the laser steady on that point for about two seconds before the artillery fires. It only really gets abusive when you set the ssm.tbl to give you twenty bombs every time it fires or something rediculous like that. If you only get one or two, all it does is save you having to re-arm so often.