For what it's worth, I liked the trade when it happened because, at the time, it looked like we were trying to build a good win-now roster. If your target is the next two years, a high-potential NHLer is worth more than a high-potential prospect. We still had Markov and Radulov, Weber was coming off a great season, defense was pretty good, Price was terrific, and Pacioretty was still an elite winger. The biggest need was more scoring, which Drouin helped address. Of course, Bergevin needed to keep going and get a top C, then re-sign the key guys like Rads and Markov. That would've been a credible direction to take and it looked like that was where he was heading.
Very possible the team still wouldn't have been strong enough, but it was a reasonable to build on the 103-point season they had, bolster the offence, and go for it, starting with Drouin. Instead, they ended with Drouin.