The only vacuum is your list of players, completely void of the context surrounding each pick. Barden pick was made in 2009 after the team had lost both Plaxico Burress and Amani Toomer. Manningham and Steve Smith had yet to emerge. They secured their top WR in Nicks who was still a rookie himself, but got Barden as insurance. You may not have liked the pick, but it fit your criteria as a glaring need that you just posted above.
Canty was a prime candidate to be a cap casualty given his number within the Giants' cap issues. It's the main reason why he never restructured. Had Austin, who was a phenomenal talent in UNC which has produced a gutload of NFL talent which hardly suggests "project", panned out, it would have been the perfect transition. Now, they were put in a position where they have a 34 year old 3T to fill the void.
Donald does fit a need. Jenkins is 34 years old. His 5 sacks sound like a great number for his position, but that hardly tells the story of his ineffectiveness at pressuring the quarterback in the first 8 games. Even if DE is more of a need, you're still suggesting to take the lesser player because of it. I don't see how Reese's strategy is questionable while that one is suggested.