"Hey Brookes, I have a big shaker of salt here. Can you hold that gaping wound a little closer?"

What the hell's the matter with you?

I think there are lots of explanations for why this has happened. Certainly the Dodgers, prior to this year, have had pretty shaky bullpens in the post season. Managers (Roberts last year and Mattingly prior) were understandably reluctant to pull him. And of course the injury stuff the last two years. But at some point you just have to say it's a thing and it doesn't matter why because it's persisted for so long. I'm as hopeful as can be that next year the Dodgers can get back to the WS and Kershaw can dominate and we won't have to talk about this, but I'm done making excuses. It's just a huge bummer.

As to the content of your post: ERAs in the post season SHOULD be worse, on average, because playoff offenses are better. So pitchers who can minimize the increase in ERA, or in the very best of cases actually decrease their ERA in the playoffs, are extra valuable.