Game enemy AI tactics

I am curious if anyone has any insight on the game's AI and equipment used when fighting enemies versus the left overs after the fight. I mean, for enemies that mostly drop only basic (whether base, fine, exceptional, or superb) weapons and armor most of the time, with the few exceptions of unique magic items, the computer enemies do some serious damage and escape damage until usually at least one play through to figure out a strategy. Only when my players get high enough level do I feel like I can just charge into combat with minimal buffs to take out certain groups of enemies.

Just curious,

Joe