Admittedly, I couldn't read this classes reading as closely as I would've liked. Doris' arguments I think are interesting, but she seems to argue that there is a mistake in calling someone virtuous in an Aristotelian sense.
Now, most of Aristotle does go over my head and I have problems understanding his entire system and while I find Doris's pyschological argument compelling I think she is wrong to say that systematic ethical systems lead to alienation. Aristotle's virtues, as I understand, do lay out some fairly explicit directives on how to deal with a situation but they almost seem to work the way parables do. By this I mean that while Aristotle might give the example (and he gives A LOT of them) of a display of courage, say in battle, there is a piece in the example that is supposed to lead the reader to phronesis. Phronesis as I understand it is no where near as rigid as Doris characterizes it. I don't think phronesis also necessarilly is simply a single character "setting" but rather acts as a sort of moral compass. It basically says that you know yourself well enough to react to a situation in the right way.
The other problem I have with situationist ethics is the notion that in a given situation our actions are unpredictable. No matter what pyschological empirical data shows I think it's a risky proposition to make. If our actions in certain situations are unpredictable how could we build a political situation to conform with this idea? Should people, since certain situations lead to immoral choices, be ethically regulated in certain instances (obviously this already occurs in things like murder, incest, ect.)? Can people be truly said to be immoral if their actions were the product of circumstance?