Hi,
is it possible that the scout is bugged? I have always felt like there is something wrong with it. Now I realised what's bugging me. Scouts scout best once they have being destroyed which is pretty weird. Have a look at the attached images and you'll understand what I mean.
I had a firebase mid and pulled my engies back a bit so that he couldn't spot my fb - I made sure that my aa would kill the scouts before they could see my t4. All in vein. The enemy did not only get to see that there are units (grey icons) but he even got to know what kind of units there were exactly. This rendered my stealth gen pretty much useless.