That's why we added that nice Rotate button to your abilities bar. We got a lot of feedback from pre-release version that didn't even know Turning was a thing.It also happens sometimes when I right click a unit and drag, to change the facing.
And when changing facing, a slight arrow while holding the right mouse button down and choosing direction would also go a long way.
If you have a attack selected it will show you the units you can hit and the likelihood through a target on the unit cards. It's not exactly the same but it should give a indication of whom you'll be able to hit.PS: The preview could even show the weapon range border from the viewpoint of the new position. What would also be very convenient.