Northrop Frye's essay, "Archetypal Criticism: Theory of Myths," in Anatomy of Criticism has often been thought provoking for me, and it helped me endure post-modern criticism. I am not particularly a disciple, but I have extrapolated often. In the essay, he divides each of the Mythoi into six phases.
In "The Mythos of Autumn: Tragedy": "The phases of tragedy move from the heroic to the ironic, the first three corresponding to the first three phases of romance, the last three to the last three of irony" (219). He does the same thing in "The Mythos of Winter: Irony and Satire," which moves to "the mythical patterns of experience, the attempts to give form to the shifting ambiguities and complexities of unidealized existence" (223). "Sixth-phase tragedy shocks as a whole, in its total effect--unqualified horror or despair makes a different cadence ... In such tragedies the hero is in too great agony or humiliation to gain the priveledge of heroic pose" (222). The sixth phase of irony, corresponding to the sixth of tragedy, "presents life in terms of largely unrelieved bondage..., and it differs from a pure inferno mainly in the fact that in human experience suffering has an end in death" (238). Tragedy is "ideal," the hero confronting "the pure laws of the universe" (Sophocles), whereas irony is "real," giving form to the complexities of unidealized existence.
OK. I think Mike is right about the ending that is bleakly ironic, as Frye uses the term common sense, morality, or expiation never figure in. The only "attractive" character seems to be Aaron, in that he takes sardonic pleasure in the purity of his evil, but, hey!, on this I will put Mike's "I do grow morally detached from people who are morally detached from what they are doing."
As to ironic detachment, I find none, despite Frye's association of his term "irony" to "sixth-phase" archetypes. Maybe that is why I remarked on how much I missed comic relief or, better, an ironic commentator such as Feste or Lear's Fool. As audience, I have no way to guess at what Shakespeare's attitude is or what my own is supposed to be (remember, Taymor's Titus is the only film during which I had to turn away from the screen), so, as per Frye, this is not satire. Yet it is a type of irony for me in that what I see and what I believe in just do no connect.
I hope I have expressed my disatisfaction with the undermotivated, characterless actions of Act I. Mike characterizes the nihilism of the end. Apart from Lucius' unresolving condemnation to leave Tamora to be eaten by birds, Aaron gets the last word: "If one good deed in all my life I did,/ I do repent it from my very soul" (V.iii.191-92). Let me quote Pope from memory: "Great Anarch, let the Curtain fall/ And Universal Darkness buries all."