I'm reading 2312, by Kim Stanley Robinson (my full review will be this Friday) but something in it is bugging me, and it drove me to write this post. That is the subject of using multi-POV with extreme emotional states. I have noticed that KSR seems to switch POVs when his characters enter their most extreme emotional states. Whenever you are in their head, they are calm. But if they freak out, you are likely to see it from a companion character. Most of the chapters so far (halfway through) are in fact duo POV chapters, which is an interesting device, but in this case I feel it's being underused.
When you're writing in third person past, you're a little more disconnected than say, first person present. But that disconnectedness offers benefits, and there are really few limitations on what kind of emotional depth you can reach with third person. This is especially true for books where the characters spend a lot of time thinking and you spend a lot of time in their stream-of-consciousness, like 2312. There's no reason why you should feel disconnected from the characters just because you use their name instead of "I."
In particular, I feel strongly that we should experience a range of emotions from our characters within their points of view, especially the extremes. One character in the 2312 in particular feels, if not completely sane then at least functioning when I'm in her head, and rarely does crazy things, but almost as soon as you switch POV she starts acting like a wild animal and doing insane things or constantly moaning. I'm not sure if this is purposeful; if it is, I haven't figured out the reason.
You don't want to have every character in your book wildly swinging back and forth between the full range of emotions like they're auditioning for some satirical director, nobody wants that. Your characters don't have to express every emotion, either; if nobody in the book experiences suicidal tendencies I'm not going to throw it away, but if they do I should be in their head for it. If they're a main POV, of course. And of course I can already think of reasons why you would break this rule, but I think setting this as the default is a good line to take. If you want to have one character rescuing another and have that help them change something about themselves, great. That puts a new focus and direction for the scene, and it's on the POV. That's different from having a POV observe another POV going nuts, and learn nothing from it nor do nothing about it. That other POV is still the focus of that scene, and you're just providing meaningless distance.
I don't think this is a widespread problem, but it's a specific one, and I think it matters. We're reading books to be transported in all our senses, and that includes emotion. Unless it's important to the plot, we shouldn't just see extremes, we should experience them.