A window team was never going to run a deeply in-experienced third pair d-corp of Broberg and Desharnais. That's simply ripe to be exposed by other teams and a detriment for a window phase team. Instead pushing a round peg into a square hole, they opted to push Broberg to a weak RD where this team's greater need for size, physicality, cycle breaking and net front support has landed with a mature Desharnais.
Again the Oilers have blown through their safety net, and although Kulak has been pretty mediocre this year, I personally doubt this team flushes a veteran defender to hope Broberg will stabilize with consistent minutes and play. Strudwick has compared Broberg to a Boewmeester type game which has driven by a simple, position based defending game; strong skating; and safe, smart play. I kind of agree with this assessment. But I also think he will grow into a solid middle pair defenseman ... just not on this team and its stage of trying to compete for deep playoffs.
Onboarding as NHL defensemen takes longer, development is not a linear process, and is damn hard.