I agree with this reading of Lise. She is one of several characters who provide an angle on Russia as a whole. I think of Katerina, the beautiful lady who lends Dmitri the money, as like a symbol of 'mother Russia', the pure integrity of an ideal, whom Dmitri loves deep down but betrays because of his shallow fickle emotion and his hedonistic preference for the tart Grushenka. So the question becomes who/what does Dmitri really love, depth of soul or shallow pleasure? At the trial Katerina behaves like a force of nature, a representative of fate who condemns Dmitri regardless of justice and truth to repay his impiety towards her.
Similarly, Father Païssy seemed to represent an authentic spirituality, expressing Dostoyevsky's own views. I may comment further on him in the Zossima thread.
Dmitri is complex. You are right that his dissolute behavior does look like a fallen nobility, with an assumption that the world owes him a living and a fury that he is not given what he sees as his by right. Maybe though, the Russian bourgeoisie also shared these characteristics, which is why Russia never got off the ground economically? It is like the sound and fury of the middle class and the fallen nobility took all the headlines but was as nothing compared to the real grievance of the inarticulate masses (Smerdy).