I'll defend the Kessel trade by saying, for every single Seguin, there are tons of Brian Lawtons, Daniel Dores, and Patrick Stefans...
Kessel was a proven high calibre two way scoring centreman with upside. Last year he had an 82 point campaign, and he's yet to score less than 30 goals since he was in Boston... Shit, when Kessel was drafted, he was touted as America's Crosby... one of the 'Next Ones' if you will. He's coming off his best year so far, and he's easily an 80 point player if he's on a team that's worth a damn.
Also, it was pretty surprising even for the Leafs that they fell so far as to give Boston a top 5 pick... much less #2. I bet they expected that pick would be #10 at the worst... and if Dougie Hamilton or Jared Knight can pan out in the NHL is still up in the air.