I rewatched that series a bunch. It's actually kinda crazy to think if Letang makes a better decision in game 5, we have a stranglehold on that series despite the issues you mentioned. I'd add collective fatigue, Sheahan almost doing things instead of Cullen actually doing things, and Murray struggling really for the first time in his career.
We have a third line. Letang is having a career year IMO. Malkin should come back rested. I worry a bit about Sid's fatigue factor, but he'll do whatever it takes come playoffs. Cullen hasn't been productive recently, but I think that changes with a healthy forward group and Blueger down on the 4th line again. And Murray's numbers since the holiday break speak for themselves.
I like our chances against any team sans Tampa and SJ. And with Tampa, I'll believe it when I see it with that group.