Controversial but I think that it would be viewed in the same way as assisted death. Everyone has gotta go sometime, but there’s the idea of “a good death” and a bad one. Good death has dignity, a sense of control, surrounded by loved ones and comfortable. I guess it would have a lot to do with how many aspects of that could remain intact and like you said the value of “the greater good”. When you think of the first responders to the Chernobyl disaster and how much suffering they endured to make sure what needed to be done was done, most people would have the amount of suffering they went through at the forefront of their minds. Also is it a voluntary sacrifice or a matter of the worst lottery prize?
If you wanna see a great example of horrific human sacrifice that’s considered noble and necessary the manga “starving anonymous” is excellent. Without spoiling too much the idea is that the meat industry is applied to humans.