I found that in patch release notes:

dna said

07-09-2015
DATA
Removed: Class-based differences in AI spotting abilities (it is covered by other systems instead)

AI spotting abilities now depend purely on the individual AI skill and the equipment available to the AI.

And I don't understand how but it made useless a lot of AI mods. AI become too sluggish. They don't want to engage enemies and wait for player to come.

Is there any way to revert that changes?