Are you guys sure? Last night, I went into a fort, can't remember which one, anyway it was goblins. My sneak is 71, level 18. I walked through the door into the secondary caverns (read: loading screen) and as soon as I entered there were two goblin shamans and one war chief, standing right there, I could touch them. Still in sneak mode, I used the shadows in this cavern, and patience, to maneuver my way across the cavern, then set up two arrow shots at the shamans loaded with poison, and when they keeled over (one shot kill for each with the poison) I pounded on the war chief. What's your guys' sneak skills?
I don't think he talks about sneaking but normal running. Sneak takes light in consideration then calculating success however I'm not sure detecting you then not sneaking uses it. Know it uses line of sight, both cover and the way the enemy is facing.
To the bandits defence on open ground you can get close enough to hit him with a ranged attack before he reacts on even then not sneaking. My mage uses this all the time.
Light should have an impact on how fast the enemy see you then not sneaking, not sure about how hard it would be for the enemy to find you, probably a bit harder but not to hard.
With very high sneak you can regularly do multiple sneak shots against enemies, work best with undead, they have problems detecting you even on five meters range.