One the one hand, writing a good AI can be difficult
On the other hand a combat oriented game pretty much requires decent AI scripts
Basically this game's combat handling capabilities have serious gaps.
I wonder if the problem is expectations: Larian's a small studio with limited resources that they have to spend carefully. I think the risk is that if they'd put more effort into combat, it would have to be taken away from somewhere else, and I think that would be at a greater cost to the game overall.
But the expectation part is what one wants from the game: for my tastes, the game is already leaning a little too much towards combat, but I guess some people would disagree; there is no "right" answer, simply a lot of different opinions. I guess I am surprised at the number of complaints about an RPG not being more combat-focussed and not being hard enough; though I am someone who tends to play e.g. shooters on easy as I'm more interested in seeing the sights and story (and who gets bored quickly if there's not much of either!)