My secondary point is that the happy ending of Apocalypse Troll was highly implausible if Dick's survival odds were really only one in a thousand. The equivalent of winning the lottery or some other deus ex machina gimmick is a poor plot technique by an otherwise excellent author. But if Dick's survival odds were more like one in five due to all the training he'd recently been doing and his foundation as an exceptional SEAL physical specimen, then the result is far more plausible. It would make sense for Milla to attempt the transfusion, yet still be surprised and overjoyed when it worked.
Even at a thousand to one, I wouldn't consider it a deus ex machina
gimmick. Dick's survival was not critical to the resolution of the main problem that the protagonists faced, it merely led to a happy ending for that protagonist. The main problem was the defeat of the troll, and the preparation for the arrival of the Kanga in 80 years. His survival or death had not bearing on either of those cases. In addition, according to the many worlds interpretation of quantum mechanics, both worlds existed, the one in which he lived and the one in which he died. RFC merely chose to describe the one in which he lived - authorial option
If you are looking for what is perhaps his only example of a deus ex machina
, look at the ending of Out of the Dark
, where the gimmick is crucial to the resolution of the main problem, and I won't be more specific to avoid spoiling it for those who haven't read the story.