When at close ranges the AI is way to slow at reacting to dangers coming out of a bush or around corners etc. This breaks immersion and makes close combat a very cheap cheat. Note that this is not a diffeculty question but instead an issue that makes the AI look stupid and ruins gameplay at close ranges. (The issue is present at all diffeculty levels, even with SuperAI enabled)
The AI needs to be quicker at shooting back if their target appears right in front of them. They should not take their time to aim but instead spray the target with less accuarcy.
To counter this diffeculty wise the AI should be less good at actually spotting targets at long ranges (their ability to hit targets at long range is fine imo)