How normal does the exclamation, "Oh, dear!" sound? (Don't forget the question structure! This is elementary-level English.) :) Yes, it sounds perfectly normal to me. I'd think the person is reacting to a little piece of bad news, or wondering what to say next.

This is a normal expression, although I would spell it differently Oh dear! I don't use it often.

I say it frequently and I hear it very frequently in the, in the - oh dear, what's the name of that country again? Ah yes - in the UK. If something is really bad, or for ironic effect, you can say "oh dear oh dear" or just "dear oh dear". I don't know if this is common in other English-speaking countries.