I would say that sneak is maybe a little overpowered, and yes, the stupidity of the AI is partially to blame, while enemies do seem to react somewhat to seeing their friends killed (Usually if I sneak attack someone while enemies are nearby even if it kills the target instantly, the nearby NPCs start looking around and I get the caution message.) it seems that as long as they don't actually find you, it's pretty easy to becoming hidden again unless you have companions who decide to attack them (as they often seem to do in these situations.) And in conjuntion with the sneak attack criticals, when using stealth I can often kill enemies before they have a chance to fight back, which isn't really a bad thing seeing as that's how stealthy characters are supposed to kill people if they need to, but the game makes it pretty easy. And with stealthboys, even if you're sneak skill is low you can still stay hidden without problems, fortunately, they're rare enough that I only use them if I really need to stay hidden but I'm not confident I can without them, like when dealing with a quest that demands subtlety.
oh and the sneak attack bonus is ridiculous. useful but, like wtf how is it harder to kill a man when he doesn't expect to be shot than when he knows he's going to be shot?
While not necessarily realistic, I'd say it's a good idea from the perspective of gameplay because it encourages players to try to take out their enemies stealthily if they're playing that sort of character, in particular, it makes it so there's actually a point in trying to be a sniper, without it, there's really no reason why stealth characters, if they want someone dead, shouldn't just whip out a minigun and blast away. I guess maybe that would be too noisy if you don't want to alert nearby people, but that's not a problem if there's no one around to hear it. Not everything in games needs to reflect real life, if it did, we'd need to actually use our skills to get better at them rather than be able to point points into any skill upon reaching an arbitrary level of experience needed to level up, whether you used it or not.
And yes, I would hardly say the game is supposed to be about realism and survival, because really, it's far from realistic, granted, if you play in hardcoe mode, you need to drink, eat, and sleep, but it takes more than that for a game to be able to rightly advertise itself as "about realism and survival", and I'd say the game doesn't offer that.