Great article, Susan, and would love to see this become a periodic column. As for the episode, it really could have gone both ways. They kill him, to reinforce the decision for the Doctor to go to his own end, to save everyone he loves and cares for from himself, and the hundreds of different kinds of dangers that he attracts, or they save him, to remind him that just because danger is present doesn't mean it can't be overcome. While the show is a bit too family oriented to hopelessly kill off a comic relief like that (usually, from my experience), there did not need to be a magic physics-breaking crack that appeared in the helmet.
We've played with the idea that an emotional surge through their metal shells can destroy the Cybermen before, and perhaps the Cybercontroller doing some kind of feedback loop into all of them would cause them to die, so I can buy that. But no amount of a primal urge to defend one's own offspring, or 'love', as they called it, can rend apart two bits of steel that appear to have been welded together. Now, had the Doctor run to him, still in the suit, sonic'd the helmet to get it off, found him unconscious, near death, and had to be carried out, to be unconscious on the floor before his son, the Doctor frantically trying not to lose someone else, reinforcing that same menace/salvation idea...that might carry the appropriate emotional weight the show is known to occasionally have. But him just springing up, being perfectly fine, and making the episode close with the emotional seriousness of a joke was not the buildup to his own death that it could have been.
We've played with the idea that an emotional surge through their metal shells can destroy the Cybermen before, and perhaps the Cybercontroller doing some kind of feedback loop into all of them would cause them to die, so I can buy that. But no amount of a primal urge to defend one's own offspring, or 'love', as they called it, can rend apart two bits of steel that appear to have been welded together. Now, had the Doctor run to him, still in the suit, sonic'd the helmet to get it off, found him unconscious, near death, and had to be carried out, to be unconscious on the floor before his son, the Doctor frantically trying not to lose someone else, reinforcing that same menace/salvation idea...that might carry the appropriate emotional weight the show is known to occasionally have. But him just springing up, being perfectly fine, and making the episode close with the emotional seriousness of a joke was not the buildup to his own death that it could have been.