Using flashlight on the battlefield is a very bad idea. Otherwise I agree that the flashlight is very dim.
In real life these flashlights have around 100 meters throw and the beam is very focused. You can change between the brightness output levels and even on the lowest setting it's still brighter than the flashlight in arma 3.
Just search for Surefire or similar well known flashlight manufacturers on the internet.

I also experimented with the AI and they are obviously cheaters.
I put three enemy rifleman 750 meters from my position which was a nice safety spot inside the woods and when I killed the first one with a suppressed m14 ebr, the other two just go prone and turning exactly the direction where I was.
They didn't shot back, but they known my exact position. In this case when I shoot from far distance the AI should search for cover, not just go prone and pinpoint me from 750 meters!!!
The AI also hear you inhumanly good from relatively far distance or maybe they just simply track you through the walls. I really hope that some AI improvement finally will happen in Arma3.