[apache]

Yep, a ship sure can turn to be able to fire all of its weapons at one target. But, it would take quite a while to do so if it had an inertial propulsion system. A dreadnought trying to aim its rear guns at an escort would have one hell of a hard time. But, again, I always assume a non inertial propulsion system in this game, so yes, they could turn pretty easily to engage with all weapons.
Now, as for Einstein's relativity, well, the fact is that this is all theoretical, not a proven fact. Just because the equations say its so does not mean the equations are valid. I will remind you that they said the exact same thing about the speed of sound, and were proven completely wrong. Yes, the equation used to calculate drag shows that as you approach the speed of sound, drag force goes to infinity. But in practice, there are more complicated effects that no one could predict until they tried and passed the speed of sound.
There is no proof that the light barrier is some ultimate all defeating universal property. The equation is actually identical to the drag equations of long ago. And think about it, if something actually were going faster than light, how could we possibly detect it?
Something else to note is that the speed of light is not a constant. It varies based on the medium it is actually travelling through. Information can definitely travel faster than light. It is possible to slow light down so much that you can actually walk faster than the beam of light.
Another property theoretically claimed by light is that it is massless. But then you have to ask yourself, how is it then affected by gravitational forces?
Now, on to the beam attenuation subject again, a laser beam will not attenuate or lose focus over a significant amount of distance in space. Right now, there are lasers with enough power to vaporize a bulldozer at 1000 yards. In space, you really would not want to get in the way, no matter how far away you are. Less powerful lasers can be used to transmit power to satellites for propulsion or simply powering a few systems on the satellite. This requires pinpoint accuracy by the laser, and it can be done. Now, yes, the beam will attenuate considerably though the atmosphere, but once it gets through the atmosphere, its rate of attenuation is approximately zero since there is nothing to cause attenuation.
Laser light is super focused, and no lenses are even used when making laser light. It is simply by the nature of the reaction itself that lasers are that focused. Also, a laser's power does not depend on how focused it is, it depends on how many photons are travelling in the beam. Basically this means that in the atmosphere, the laser light will attenuate severely as the photons are reflected off or absorbed into the air molecules. In a vacuum, there is nothing to diminish the power of the laser, and so the beam diameter at a long distance, though still almost exactly the same as it was when the laser beam was generated, will still be carrying the same amount of energy that it had when it left. What does it mean? It means that if you fire off a terrawatt of power in a laser in space, you can be sure a terrawatt is going to hit something (and probably blow it up since a terrawatt is a ridiculous amount of power).
Now, one other point to make, none of the beam weapons in the game are using light as their main energy form. They are all using subatomic particles. There is, sadly enough, no laser weapon in the game.
But yes, when it comes down to it, it is a game, and we are all nerds for even trying to explain it realistically.