I know it's the fun thing to do on HF is to make fun of Dubas, but honestly he's done a good job in Toronto, both in terms of identifying areas of weakness and addressing them, and identifying "cheap" options to fill out a lineup's depth with limited remaining cap space.
When he first got to Toronto their blueline was their clear area of weakness. He's since added Brodie, Muzzin (hurt now), Giordano, and McCabe. Their defense may not be top 5 in hockey still, but it's been vastly improved from the one he inherited.
He also has been good at finding bargain contracts that actually produce. Bunting is producing like Bryan Rust/Jason Zucker but for around $900k per year. Jarnkrok paced for over 20 goals this year for half the cost we're paying guys to produce that. David Kampf is the kind of defensive gem that Sullivan absolutely loves burying in D-zone minutes and is making $1.5 million.
Plus, the idea Toronto was too "soft" for the playoffs, at least Dubas has tried to rectify. Some misses (adding Foligno for a 1st), but some look to be good additions like O'Reilly and Acciari.
Every GM is going to make mistakes or whiff on some moves. But the difference between Dubas and what we've gotten in Pittsburgh lately is he has a clear vision and he also sees what his team's weaknesses are and actually addresses them rather than just operate around the fringes.