I mean according to the last list I saw the worst trade in Braves history was a Texeira trade where none of the pieces traded actually were missed in the MLB lineup (though Feliz certainly could have been a nice set up man to Wagner/Kimbrell).
Some people cannot stand losing perceived opportunity cost. They always want to give up nothing to get something.
Now, I think you should not cash chips in until you are close, but I'm willing to trade away players to try and win the whole thing. that's the point.
The point of trades is to get value for the assets you have, not to trade them because they are blocked. The Braves had Chuck James, Buddy Carlyle, and Kyle Davies in the rotation (Reyes too) and decided it was a good idea to deplete the farm for a bat.
As for you point on the players, they certainly could have used Feliz and Harrison. I was always in favor of moving Salty or McCann to first base, which could have allowed them to focus resources on adding an actual arm since they were delutional enough to think they had a chance at competing that year.