It would seem that the Nazgul effect a loss of perspective, and their victims despair no longer being grounded in a reality, but lost in their own darkened distorted thoughts. (Sounds a lot like major Depression, doesn't it?) This makes me question whether the scent each patient smelled was not what they yearned for, but rather what might comfort them, whether real or imagined. Perhaps then Aragorn guessed that these were the scents best suited for each. Being knowledgeable in history and well traveled it would seem possible, and I think I might be reiterating the thoughts expressed earlier.
Formendacil, I do like the idea of Aragorn’s humility prompting him to remove the star, but it still strikes me as sad. Perhaps it is intended to, I don’t know. But the mention that Gandalf had to beg him to enter the city, and that he obeyed in order to help was very moving, although the practical side of me was wondering were Andúril was at the time, for it was said that he didn't have any tokens of his claim except the Elessar.
One more thought about Frodo’s illness, if you will indulge me, I am wondering if Aragorn might have sought Elrond out to learn more of healing such maladies as Frodo recovered in Rivendell. If that were the case the hobbit might possibly have helped the king in a round about way, though at the time it was harrowing.