Yawn. We've been over visibility already.
People trying to defend easily capable gimps here is almost as sad and pathetic as what happens when a skilled player starts schooling people on traps. Specifically, by ignoring them, instead of wasting time and resources on them. And people feebly cling to traps, and make all manner of crazy statements to try to defend traps simply because it's all they know.
Same for scouts.
And to the guy who tried to bring military strategy into it: Lol, what?
Military strategy, on Earth is low level humans vs low level humans. Because that's what we have and fight here. The D&D world, obviously is not limited in this way. Modern military strategy has no answer for an Ice Devil. It has no concept of an Ice Devil. It doesn't even know what a fucking Ogre is.
You see, worlds that are drastically different evolve in drastically different ways. The military strategy, in a D&D world is a team of state sponsored superheroes, vs their team of state sponsored superheroes. Fuck armies. And when that team of PCs runs across something, chances are they don't have any fucking warning, and they don't get any fucking warning from mundane scouts in a world where all manner of creatures can make anything alive glow like a streetlamp, or instantly become aware of any minds within range, or sense a disturbance in the Force, or feel the quivering of approaching footsteps, or even something as innocent as the nose of a bloodhound, but the mind of a man. And if they have those things, themselves, then the result is that they both detect each other, but since the scout is alone he gets slaughtered... or you take the hint, don't scout, don't split the fucking party, and don't take a goddamn walking dead man (not to be confused with Undead) along to leech your XP and treasure. Then you either auto detect the enemy as they detect you, or not, but at least you're all there to fight the damn thing.