The argument re Letang has ALWAYS been - do his positives outweigh his negatives (obviously taking into account the high price tag/salary).
As a goalie, I always come down on the side of "it's not the ones you stop, it's the ones you let in", the lesson being that a bad goal/bad play/dumb mistake always has a larger negative effect on the team than the supposedly off-setting brilliant save/fabulous play/amazing goal.
It's because the negative plays can set off cascading issues, where players lose trust in the goalie/defenseman/whoever , start over-compensating, chasing pucks, losing position and on and on.
For this reason I've never been a fan of Letang, even though his brilliant skating/transition work obviously has been a real positive. And clearly his crazy athleticism has for years allowed him to recover from serious blunders, get back, break up plays, and save a back-breaking opposing goal. Sometimes.
But as Billy has warned us for ages, these types of players do not age well. And that is what we're seeing now, as Letang loses a step, and his athleticism slowly diminishes. We may even be seeing more of it because he's clearly been told to play in a way that doesn't come naturally to him, which seems to make him think too much out there, with brain-cramp mistakes the result.
Anyway. Even years ago I was not convinced the positives outweighed the negatives.
But I think it's pretty obvious which way things have tipped now. He's been directly responsible for crucial game changing goals in 2 losses, in a tight series with near-zero margin.
I hope JR has the cojones to make a deal this summer.