Kibou: I'd say the missing finishing moves are definately intended, since they would require additional animations. I also think that the inability to roll is by design, although I have to admit that it doesn't make sense - performing those rolls should even be easier empty-handed.
The part with the higher damage is quite interesting. That explains why those drug-making bandits in that cave killed my so easily until I figured out there's a sword to grab nearby. =)
Maybe that's supposed to emphasize the importance of weapons - after all, Witchers are trained in swordplay, not martial arts.
I've added the bug to the list, so maybe some day a dev might read it and explain the reasoning behind this handling. ^^
I think the issue was that since the state of being unarmed happens so rarely, the devs probably didn't pay much attention to it hence the design oversight (for lack of a better word).
About the finishing moves, I am thinking about the same thing. But I have seen Geralt doing one-hit-kills with sword without triggering the finisher cutscenes (on rare occasions though)
As for that particular quest, I guess the "intended" way is to grab your equipment from a chest quickly and kill the bandits.
I know that Witchers are supposed to be fighting with swords, but any regularly trained soldier would have at least some decent unarmed skills.