Jigsaw: Hello, Agent Strahm. If you're hearing this, then you've finally found what you've been looking for. But is the discovery of my body enough? Or will your insatiable hunger to uncover the truth push you deeper into the abyss? Heed my warning: do not proceed. For this room can either be you sanctuary, or it can be your grave. The choice is yours.
Agent Strahm: Fuck you.
Brit: No it's not Jigsaw, he's dead. Haven't you watched TV lately?
Jigsaw: Murder is distasteful.
Jigsaw: Hello Seth, I want to play a game. Right now, you are feeling helpless. This is the same helplessness you bestowed onto others. But now, it's unto you. Some would call this karma, I call it justice. Now you served five years of what should have been a life sentence, for murder. A technicality gave you freedom, but it inhibited you from understanding the impact of taking a life. Today, I offer you true freedom. In thirty seconds, the pendulum will drop far enough to touch your body. Within sixty seconds, it will cut you in half. To avoid the pendulum, all you have to do is destroy the things that have killed... Your hands. You must insert your hands and push the buttons to start the devices before you. Your bones will be crushed to dust. Will you destroy the things that have taken life in order to save one, Seth? Make your choice.
Answer: The games of Jigsaw and his followers were always intended to be extremely difficult, but with a small chance for survival based on the actions of the player. Hoffman probably wouldn't have cared either day if anyone else survived, but likely anticipated that most of the others would die. (Strahm's line about everyone being supposed to die with Hoffman being the soul survivor was more conjecture than anything.) In terms of killing Jeff- both Jeff and Strahm were emotional hot-heads, so in all likelihood one or both was going to die if they encountered each other. Strahm's water cube was intended to be an execution tool for breaking the rules. That's why Hoffman seemed so shocked that he miraculously survived.