Like 4 people die between Mortal Coil and the series end. -Some unknown dies in "One" when they enter a Nebula. -2 unknown crewmen die in "Equinox," killed by the aliens. Seven and the Doctor are not even aboard Voyager to attempt a "revival." -Carey is killed on a planet with no hope of revival. If we include Lyndsay Ballard that's 5, but I don't know if that takes places before Mortal Coil or after. She also died on a planet or in a shuttle. If there was a candidate for seven's "treatment," it might be the one who died in the nebula, but we don't see them, and can't know. She can't just revive anyone, and only has a short window of time to do it. The girl that the EMH let die to save Kim died before Seven was on board.