The current reaction fire mechanics are a hack because the aliens don't have proper AI yet. As are the alien LOS mechanics, as you guys have already picked up on. I think aliens have pretty much unlimited sight range and 360 degree angle reaction fire.
The scout should work fine in the next update. I admit it's going to be hard to test the weapons properly until the aliens have some proper AI, but we're looking at AI coders at the moment so hopefully it won't be too long.