There's a reason it's called heroic responsibility: it's for a fictional hero, who can do Fictional Hero Things like upset the world order on a regular basis and get away with it.

NO! This is clearly not why it was called heroic responsibility and it is unlikely that the meaning has degraded so completely over time as to refer to the typical behaviour of fictional heroes. That isn't the message of either the book or the excerpt quoted in the post.

Which you very much do. You don't need heroic rationality, you need superrationality, which anyone here who's read up on decision-theory should recognize. The super-rational thing to do is systemic effectiveness, at the level of habits and teams, so that patients' health does not ever depend on one person choosing to be heroic.

Those who have read up on decision theory will be familiar with the term superrationality and notice that you are misusing the term. Incidentally, those who who are familiar with decision theory will also notice that 'heroic responsibility' is already assumed as part of the basic premise (ie. Agents actually taking actions that maximise expectation of desired things occurring doesn't warrant any special labels like 'heroic' or 'responsible'.) Harry is merely advocating using decision theory in a particular context where different reasoning processes are often substituted.

An optimal health system does not sound melodramatically heroic: it works quietly and can absolutely, always be relied upon.

Harry knows this. If Harry happened to care about optimising the health system (more than he cared about other opportunities) then his 'heroic responsibility' would be to do whatever action moved the system in that direction most effectively. The same applies to any real humans who (actually) have that goal. Melodrama is not the point. (And the flaw in Harry that makes him Melodramatic isn't his 'heroic responsibility', it's his ego. A little more heroic responsibility would likely reduce his melodrama.)

The fucked-up thing about children's literature

You seem to be confused either about which piece of literature is being discussed or about the target audience of said piece of literature.