Hearing doesn't work as a "cone" and considering peripheral vision and simply turning your head to look around, the vision "cones" are way too narrow.

It's taking them so long to develop a sensible stealth system it's almost like they think this version is great. Screw the D&D skills and use Larian's own fun cone mechanic instead, right? Stealth skill is only a secondary consideration if you fail at the fun stealth minigame that ignores a characters skills completely.