Dryden's story of the joint tragedy of Antony and Cleopatra (and Egypt) titled All for Love with the subtitle The World Well Lost is a poignant Restoration tragedy that shows the hero realizing that even at his most successful, his qualities were not adequate to the needs of the moment, (e.g., his victories against Octavius were minor ones). In Dryden's tragedy, Antony loses his major confrontation with Octavius in large part because of Cleopatra's actions and cowardly behavior. When Antony comes out of seclusion in the temple of Isis in Alexandria, he says in front of Venticus, his trusted general, that he curses the day he was born and he and Venticus weep together over the reality that Antony destroyed much of the Roman Empire because of his love for Cleopatra. It was said that the Roman Empire covered "the world." This then is the source of Dryden's title All for Love; it lies in Antony's confession that the Roman Empire was devastated by his love for Cleopatra.
The subtitle contains a play on the word "well" that makes it an ironically befitting addition. At first reading, The World Well Lost seems a calloused praise of the blindness and folly of love. In the most common sense, "well" means to do something in a good or satisfactory manner (Dictionary.com). However, other meanings are "certainly; without doubt" and "fitting" and "thoroughly." When "well" in the subtitle is considered in light of any of these latter definitions, a picture of ironic finality emerges that is absolutely in keeping with Antony's thoughts, feelings and end. Yes, I'd say that the subtitle is apt, indeed.