There is a problem with AI sight and behavior. I'll use a video as an example.
In the first part, i'm not detected, that's ok. Enemy soldiers look calm, they don't expect me, so the probability of my detection is zero. This works fine. But in the second part, i'm in very similar location and the enemy soldier does spot me. What's his reaction? He tries to shoot me, then he does some weird maneuver and comes at me again. Alone.
Now, there are some major problems. My hiding spot in both scenarios were very similar. Yet, i was detected in one case. Since this is a game, there should be some rules. I have no problem with the game to be difficult, but i think that you should know what's safe spot to hide. Now it's like sometimes grass hides you, sometimes it doesnt't. Sometimes i was detected even when hiding behind a bush. This can really destroy whole gameplay mechanics (in fact, i think it did in arma 2, where enemy could easily spot you from 200m in 3:00AM without a night vision), because you can spend 5 minutes crawling through tall grass and some random soldier 300m far will accidentaly spot you. Even in old Operation Flashpoint were pretty clear rules(inside a bush = hidden) and it worked. I belive it's better even to dumb the AI down a little bit than trying to make it 100% realistic. It's a game, so please set the rules and let us play by those rules.
Second problem is lack of cooperation. If you see enemy soldier, the first thing you would do is to report to your squadmates. But you can't just follow your target alone. And his squadmates should notice he's shooting.
On the other hand, the AI is much better compared to ARMA 2. Please, just fix the AI sight issue.