So I read the issue and here are some thoughts.
First, The death was The Human Torch, Johnny Storm. However, he did not actually die in the comic. The last we see is him fighting an army of hundreds of thousands of Annihilus's soldiers in the Negative Zone. Annhilus is right there as well. Basically the chances of him winning are 0. However, we do not see a body. We do not see him ripped apart or anything of that sort.
Rules of Comic book death
1. No body, no death.
2. Even with a body, they may come back.
So why is Marvel touting this as a death? Simply because for the members of the Fantastic Four and the other heroes of the Marvel Universe, he is dead. We in the real world know he will be back someday. They, however, do not know that.
So why do it at all? Well for the next few years Marvel can explore stories of the surviving members and how they live without Johnny. The FF, unlike other teams, is a family, literally. The last few years of FF stories have been good. And someday Johnny will be back.
This death was not done for shock value. We knew it was coming. Of course we did not know which was going to die. Shock value would be something like the death of Ares during Siege. Now there was a poorly written death story.