Let me be devil's advocate for a moment here, Nepenthe.

Let it go on the record that as much as I suffer from the assassinate skill, and will continue to suffer because every other character I play these days isn't a duergar or a polearm spec... I don't really care whether it's changed one way or the other. If I get assassinated I'm going to be pissed with myself for letting the person get the stalks, not pissed with his luck or the skill itself. Sometimes I gamble and use assassinate as a way to force an assassin to step out of hiding and fight me because of it's all around low success rate. But if you're dealing with an assassin that has more than a 90% in the skill, that's dumb. (and it's fairly easy to tell whether that's the case by paying close attention to know how long ago the assassin STARTED stalking and whether he succeeds on you or not. If it seems like it was less than ten stalks and he succeeds, then yes using assassinate to force him to toe to toe you is ####ing retarded.)

What reason is there to allow someone to be assassinated while they're hopped up on adrenaline? i.e. letting the assassin get those stalks but then spam assassinate until the fight breaks off?

I would think that if you're on edge, it's much harder to be snuck up on after a fight with a mob or player. It goes under the same principle, IMHO as the sleep tweak, if you save against a sleep spell, you're on edge and it's harder to put you to sleep. So wouldn't that mean it's also harder to succeed in blackjacking and/or assassinating?

I'm not saying this should be harder during a fight (for the skills that are possible while people are fighting) but if a fight breaks off i.e. you or an opponent flees, you're definitely checking your surroundings, provided you're not lagged by something like bash.

Game balance?

As I said, I'm only playing devil's advocate out of curiosity. I could give two ####s about whether it's easier or harder to be assassinated/slept/blackjacked because if I really have an issue with a rogue class, it's time to find a duergar anti-paladin friend to gang them with, or in the case of a necromancer that is sneaking or I just can't find a ####ing way to get them before they get me, it's time for more svs spell.