People with severe influenza certainly do feel like they are dying because of the muscle and body pain as well as high fever. I would say that if a person with flu develops breathing difficulty, fever >104, or is coughing up blood, they should seek medical evaluation. Try to keep in mind that the vast majority of people who develop flu recover without problems. Dropping over dead because of the flu is not the norm.
The oddest thing ( for us ) about this season's bout is that there was no warning. Usually when we get it we notice a sore throat, stuffy nose or something that tells us something is going on. This time the kids just woke up with the high temps and severe headaches.