you have a point about the death part, Goody2shoes. i see it this way: even though we think we are seeing Statine dying, and in fact it is what is happening, at the same time it is a concept showed through dance moves, artistically and not realistically. its like two faces of a coin. on one side there's cinematic reality (they show what happens in the movie). on the other they're expressing the tragedy of it on an abstract level (as in modern ballet). this contradiction allows them to do the unrealistic moves that you mentioned. Tessa can't move that way as a dying person, but she can if we take it as an artistic rendition of her death.
it seems they're going to change it, so what we'll see in February may be totally different. as it is now, i think its in the spirit of the movie. Satine coughs while singing Come what may on the stage, but her collapse right after the final curtain is still kind of unexpected. so everything suddenly ends in nothing. all the chaos heads nowhere.
now that i think of it, the Come what may chorus part of the routine could be a reference to the 'love's triumph' which occurs on the stage when Satine calls back Christian and the duke is defeated. then her death shown right after would be logically linked to that part.