Another thing that pisses me off about the enemy AI in this game is how they magically appear behind you. This has got to be one of the cheapest and laziest ways to make a game more difficult. It's so fucking frustrating. If I clear an area, I shouldn't have to worry about enemies spawning behind me out of thin air who will then shoot me in the head with pin-point accuracy when I'm completely occupied by shooting the pin-point accurate enemies in front of me.
There should be a set amount of enemies per area. If you and your team are good enough to clear everyone out, then you should be able to carry on with the rest of your objective without hassle and not have to worry about enemies materializing out of thin air. And it's not just from behind you, either. I've watched so many enemies spawn in front of me. I was just doing the mission where you have to collect the packages at four locations in a set amount of time, and I was on the last location shooting some triads behind some wooden crates. I finish killing those guys and shift my attention to the guys on the rooftops...and the guys I just killed next to the wooden crates were replaced with a new set of enemies who then proceeded to kill me. Right in front of my eyes. It's fucking bullshit.
I fucking love this game, and it won't put me off from carrying on playing the online, but Rockstar have really disappointed me with the way they've handled their enemy AI. It's an area that really needs an overhaul imo. I should be killed for making stupid decisions and not being on top of my game, not because the game spawns infinite enemies in places I've already cleared.
