Yes, unfortunately, Hange met their end in the manga. It was a poignant moment for fans. The circumstances leading to their death were quite intense and had a significant impact on the story.
Their stories provide first - hand accounts. It's one thing to read about the numbers and facts of the genocide, but hearing from the survivors makes it real. For instance, they can describe the atmosphere during that time, which textbooks can't fully convey.
A 'genocide graphic novel' can contribute by making the concept more accessible. The combination of images and text can reach a wider audience, including those who might not be inclined to read a long, dry historical account. It can also make the horror more immediate and visceral, which is more likely to stay in people's minds.