...up to the radius of the spell, and from the point the bufee places the center of the spell within that radius, they can see/hear (depending on spell) a certain distance based upon degree of success (number hits) and magic of caster....
Small correction; I think the intent is that the radius around the subject where the location of the 'bubble', or the 'spot' as they call it, can be placed is limited by the detection AoE (which is equal to the casting magicians Magic + the casting magicians net hits, rather than the base radius of 2 meters of AoE spells), and that the base radius of the 'bubble' you can actually hear or see within is 2 meters (but can be increased with the Increase Area spell adjustment, rather than being based upon magic + net hits as you wrote). Also that the whole 'bubble' (not the radius around the subject where the location of the 'bubble' can be placed) may be moved at any time with the Shift Area minor action adjustment.
How would the ability to scout around corners, at a distance, not be helpful? Potentially scouting entire rooms as well? What am I not seeing here?
I think they are comparing it to previous editions where you could move the point of origin of your 'eyes' some 200-300 meters away from your body and from there have regular line of sight to let you see 'distant' things for real - to this edition where you instead replace your regular line of sight vision (that can potentially see everything near your body up to perhaps several hundred meters away) with a limited 2 meter radius 'bubble' that severely limit your situational awareness and that may only be moved up to perhaps 10 meters away from your body.
Will there be situations where it might still be considered useful? Sure.
Is it 'as useful' as it used to be? Hell no :-)
In many cases you can probably use an endoscope (or mage sight goggles, or a periscope, or a micro drone) instead.
...do believe the spell could be detected if someone is astrally observing, since it's a small astral aura moving about, but it's far more subtle than an astral projecting mage and not vulnerable to astral attacks: worst case you trigger an alarm, instead of having three astral entities tear you apart.
Don't active magic (such as the 'bubble' with a 4 meter diameter you are moving around) even have an actual tangible astral 'form' on the astral plane (similar to a projecting magician), not just an intangible 'aura' (similar to that of a mundane object). If so, it will not only be immediately obvious on the astral plane it can also be 'attacked' on the astral plane (via dispelling and possible also via astral intersection).
Your first and best defense when it comes to noticing magic is other Awakened people. The spell that is hidden in the physical world tends to light up the astral like an oil lantern, or a commlink on its brightest setting, or whatever other light source you’d like to imagine. A teammate who can see the astral is a considerable advantage in the sensing magic department.
...but yes, a wholly astral entity can't use it to directly attack the subject of the detection spell. So in that sense it will for sure be more 'safe' than opening up the mind to attacks from the astral plane by using astral projection.
I wonder if the intent for this edition is that you would have to 'press through' astral barriers (such as a Ward) in order to move the Clairaudience or the Clairvoyance 'bubble' inside / behind them.