My initial reaction to this movie was that it killed off main characters almost casually, and for no narrative purpose. However, the consensus of the fans at this marathon was that there was a narrative purpose: motivating the subsequent bravery of the remaining characters.
I still disagree. After all, those same characters did equally brave things in some of the episodes.
I think the big temptation in any kind of artistic criticism is to assume tragedy has greater depth than it actually merits. I think this stems from the fact that when you have an emotional reaction to something, you tend to assume there's a larger purpose ... even if there really isn't :)