One of the saddest "deaths" in Doctor Who history is when poor D84 sacrifices himself to destroy SV7 and any other robots within his vicinity by activating The Doctor's robot destructor. It's heartbreaking when he says his final words of "Goodbye, my friends", as there is a tinge of sadness in the robot's voice. D84 has probably been my favourite thing about The Robots of Death (apart from Pamela Salem's cleavage...). His response to Leela's spontaneous attack on him ("Please do not throw hands at me.") is just brilliant. As I said before, D84 could have been a unique companion, and it's a shame he wasn't kept on in some way.
However, D84 is one of many victims in a grim story where there are no fantastical deaths by ray gun. Virtually every human character is strangled to death. Death by strangulation seems to be almost a common theme in the lives of the humans in this story, as it also serves as a source of black humour amongst the characters, and the deaths of such characters as Chub and Cass are treated with little shock or emotion. Such is the overall impression that The Robots of Death leaves - death as a way of life. There's little room for remorse at the end of the story, no resolution to what happens to the only three survivors (Uvanov, Toos, and a mentally damaged Poul), and The Doctor and Leela merely shuffle off back to the TARDIS and flee the scene before any further questions are asked.
I like The Robots of Death, but not nearly as much as those who claim it to be one of the top ten stories ever made. It looks superb, it's wonderfully acted and directed, and it contains some of the best dialogue not written by Robert Holmes. But it is, at it's heart, a run of the mill, base under siege story that just happens to be presented with a unique visual and artistic flair.