I like the idea in general, but I'm not so sure about the parry option. Namely, it looks as if it's "tied" to a particular situation too much, and there's absolutely no reason you wouldn't want to use it in such situations; in that case, parry is just another button you have to press before doing X, making it redundant in a way. Of course, "run away" isn't the only situation such an option could be useful for: the poison thing you mention is one, as could be a scripted sequence where you're defending a gate waiting for reinforcement, or you're trying to draw attention of a particulary dumb creature (some sort of Mire Troll, maybe?
) to yourself. Still, what all those have in common is that you'll want to use parry and nothing else.
The power/finesse abilities could work just fine, though I doubt the numbers as you put 'em will be appropriate (as mentioned already, the ToHit bonus is preferred in most encounters) - of course, that's a thing for beta testers to... well, test. I also doubt bonus differentiation by weapon would be a good decision, simply because it adds needless complexity (not to say such differences are a bad idea, they're just more suited for a game with a slightly different focus).