Yeah, enemy units seem completely deaf, and lack any real peripheral vision. We're not sure what the developer team is thinking with regard to stealth, they haven't said a word concerning it. Maybe they'll rework it, maybe not. At present, I just don't use it, the system is beyond broken. The only rationale I can come to is that it is intentionally broken. Meaning, it's a difficulty release valve, so the player can cheese the system when they're having too much trouble with an area. It's literally an "I win" button presently.