The so-called "Tyler" trade will never pay. The main reason for this is that if you are a believer of the 'Sam Pollock' rule where the team who gets the better player is the winner of a trade, none of the players they got from Dallas for Tyler Seguin will come close to be as good as he is and will be.
The 'Tyler Seguin' trade may one day be regarded as being as worse as the 'Joe Thornton' trade. These types of bad trades often wind up hurting a franchise or slowing its progress for years. What counters that lack of progress are other trades that wind up being heavily in that team's favor. Getting Tuuka Rask from Toronto in exchange for Andrew Raycroft was the type of deal that sometimes saves a franchise. It was a trade that lessened the impact of the awful Joe Thornton trade with San Jose. As awful as the Thornton trade was for the Bruins, it turned things around in San Jose & from that day made it a model franchise who competed year after year since the trade.
Another trade that lessened the impact of the Thornton trade was getting Zdeno Chara from Ottawa. Chara was among the league's top defensemen for several years once that trade was made. Ottawa chose to keep Wade Redden & let Chara go. They couldn't afford to pay both at the time. Ottawa could have been one of the league's top franchises for a decade had they chose to keep Chara over Redden.
I won't pin the blame for the Kessel trade solely on Peter Chiarelli. They couldn't come to terms with Kessel and felt they'd be overpaying him if they gave in to his demands. His situation was similar to P.K. Subban's situation a couple of years ago where he refused to sign a bridge contract, preferring to hold out for a multi year contract. They both played chicken and Mtl wound up winning by signing him to a bridge contract. However, 20/20 hindsight now shows us that had they chosen to give in to Subban's demands at the time, he would have wound up being a bargain for them instead of now having to pay him $72 million for 8 years.
We also now realize that Kessel would have been a bargain for them had they chosen to sign him to a long-term contract instead of a bridge contract, which they wanted. But they weren't sure how good Kessel would become, plus the fact he was just getting over a battle with cancer. Boston did the best it could by finding a team who wanted Kessel in exchange for two first-round picks and a second-rounder. The players they wound up drafting were Tyler Seguin, Doug Hamilton & Jared Knight. They gave up on Seguin with two years, Hamilton will be a pretty good defenceman (but the Leafs never would have drafted hiim), and i've never heard of Jared Knight.
Seguin likely would have been a disaster in hockey-crazy Toronto (his hometown on top of that) due to his immaturity and the Leafs likely would have wound up trading him like Boston did. But there is no way Boston will ever come out winning the trade they made with Dallas. Seguin is and will always be the best player of that group, period. But if Seguin really had to be moved, Peter Chiarelli did the best he could considering the circumstances. The players he got from Dallas were decent players. But did he give up on Seguin too soon? Who knows. Playing in Dallas is quite different than playing in the limelight of party-town Boston. If Seguin becomes a superstar in Dallas, it doesn't mean that he would have been the same player in Boston for the reasons i mentionned.