Just to clarify: By 'pain' I mean the hurtful aspect of the sensation, not the base sensation that could remain in the absence of its hurting.

In your first paragraph you describe people who take pain to be instrumentally useful in some circumstances, to bring about some other end (e.g. healing) which is itself good. I take no stand on that empirical issue. I'm talking about the crazy normative view that pain is itself (i.e. non-instrumentally) good.