Hah. I've had that happen a few times, too. Heck, one of my biggest complaints about KotOR, in fact, was being a Scoundrel/Consular and getting ready to sneak up to the Mandalorian Captain on Dantooine. I was absolutely sure I couldn't take him in a fair fight, so I was sneaking up for the mother of all sneak attacks. My party was back a ways away, well out of reach.
And of course, as I got close... cutscene. I drop out of stealth and walk in for a meaningless conversation ("So you're the Jedi who's caused so much trouble. This should teach you a lesson!"), and then I get my butt handed to me because, well, no sneak attack, and my followers are half a mile away.
I will do everything in my power to make that NOT happen in one of my levels. MAN, that ticked me off. I almost prefer the simplicity of Jade, where you don't HAVE stealth, so at least you don't try to set that stuff up.
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I don't think that the encounter triggers are the worst issues in NWN2 -- I think that the UI and AI issues trump those -- but AI and UI issues are programmer things a lot of the time, things that the designers don't have a whole lot of say about, or they HAVE that say, and that say gets ignored.
Encounter triggers, though? That's easy. >I< can do encounter triggers. If I can look at something and say, "I personally could have executed that more effectively," about a particular design issue, that's pretty bad. Unless it involves the proper use of adverbs, I shouldn't be able to say that very often.