My only other complaint about the episode is the depiction of the hallucinatory Ee'char. It's such a Hollywood way of depicting an emotional crisis, to have a character imagine another person to have conversations with. Sure, I have imagined conversations from time to time, but I've never actually imagined the person in front of me while doing it. Maybe people with PTSD see such visions, I don't know, but I felt it cheapened the episode a little.
I think this is done because it's an easy way to show what the person is thinking and feeling on a TV screen. Have them talk to a person that's "in their head" as a way of verbally working out what's going on inside of them. If we were reading a book about O'Brien's experience, Ee'char wouldn't be necessary.
And I do agree with you, the way this episode was never even mentioned again was very TNG. I would have expected DS9 to let Miles be a bit "off" for a few more episodes at least.