I wonder if companion control is part of combat mechanics.
Naaah.
The AI is how the AI deals with combat mechanics. If the mechanics are there but the AI can't handle them properly then that's not the fault of the mechanics, its the fault of the AI.
The fact that you're relying on the AI to play the game for you already demonstrates that single player combat is subpar. Not only is the AI kinda shitty, but their shittiness is not an impediment to succeeding at Neverwinter Nights. Even if the AI was great it wouldn't make the game any good, the same way the gambit systems from DA:O and FFXII don't make or break their combat systems.
You seem to be confusing people who fanboy D&D with people who fanboy NWN. The people who can cope with shoddy companion AI are not praising NWN as a standalone entity, they are praising its implementation of D&D mechanics.
In comparison to other game's attempts at implementing D&D mechanics it comes up above average. If you want a game with good D&D mechanics then NWN is a good example.
However, you're making rather irrational comparisons to all kinds of other RPGs that, to be honest, have fuck all to do with D&D.
It's extremely simple:
NWN has appalling companion AI.
That's it. That's all there is to it. The codex top 50 games is absolutely littered with games that completely suck at one particular aspect, but get a pass. But you, for whatever reason, wont allow this game to pass. You're welcome to have that opinion, but there's no need to dress your opinion up as some kind of definite objective fact which requires 200 pages of hyperbole to cover up. You personally don't like the shitty companion AI in NWN and you can't be arsed to try and mitigate it, for whatever other undefined personal taste issue you have.
You're being like the retards who refuse to respect IE games because they have bad pathfinding. You know, that one Achilles heel that somehow makes an otherwise competent game suddenly unpraisable cos of that one tiny little thing.
The OC to NWN didn't help matters by being more boring that watching paint dry. I mean, exploring the sewers for hours on end in a fantasy RPG? Maybe in a Fallout-like game, but in a fantasy game, and with no interesting sewer-based monsters of fantasy. Jeezus, just give me a sedative, its quicker.
However, once the game is actually interesting, or relateable to normal D&D fantasy, such as the pure dungeon crawl Hordes of the Underdark, then the problem of companion AI is but a small and relatively insignificant element to the whole. The mitigating is simply:
1) Play on default settings and allow your companions to get up after combat without Resurrection and enjoy the game for the companion related talky what-nots. If you don't want a game where you just 'do stuff' while your companions boot-up their next dialogue options then there are tuns of cRPGs you probably wont like, its a distaste for a genre rather than a factual problem with the game.
or
2) Set the game to regular hardcore rules and don't care about companions and treat the game like a single character D&D adventure. If you want to get in a paddy about not wanting to play a single character D&D adventure, then that's just personal taste, there's nothing factual there to be discussed.
And under both conditions you have an above average, competent, cRPG.
Amazing isn't it, you're bitching like its DA2 level of diarrhoea when, in reality, its just another slightly flawed gem, like pretty much every game the codex praises. Except this game had D&D, which, theoretically, should give it more support round here rather than less.