A story can't sustain a constant level of rising tension. In other words, it can't go up like a slope. Rather, the tension has to increase like a staircase, one step at a time, then give a little breathing room before going up again. Otherwise, it all becomes overwhelming.
The light moments are little places to relax. Sure, the squirrels are silly, but the bard they're listening to is struggling to write a song about her teacher, who was slaughtered by gnolls.
Anyway, I guess I'm saying it's all a balance in storytelling, and I don't think they're doing a bad job at all. I like that the game isn't afraid to go dark, and I appreciate that the game remembers there's a bit of light from time to time, too.
