Yes, Dobes looks like a future NHL goalie, but the Habs obviously aren't fully confident in him yet, which is why they've been overplaying Montembeault. That decision has created a lose-lose situation where we're not getting the best from either goalie. We're overworking Montembeault and underworking Dobes, which doesn't help either of them.
If the goal of this season was the playoffs, then getting a veteran backup would've given the team a more confident option, allowing them to rest Montembeault when it's best, instead of only when they have absolutely no choice.
To be clear, I'm NOT saying we should've gotten a veteran goalie. The playoffs may be the immediate goal, but they shouldn't be sacrificing the greater goal – longterm development and progress. Which is why I think they should play Dobes, mistakes and all, so that he'll become a better goalie next season and beyond, when we really need him.