the complete lack of correlation between WCV powers and aneurysms mostly(or build up of symptoms for such). Nobody bleeding out their nose in WK, no mention of it being possible when Thomas almost kills Justine, ect. "When we rip the life force from someone it causes brain hemorrhages" In real life, we have people die mysteriously all the time, natural causes, ect. No reason to invent something for what would look like a natural mystery as apposed to supernatural. Covering up bite marks and drained corpses is more on the that line of thought.
Yes, people do die of natural causes, however in the case of Malcolm, who was from out of town, most likely middle aged at best, that diagnosis wouldn't be put on his death certificate without evidence, known medical history etc. There are no "bite marks or drained corpses" left behind when a WCV is done. I don't know about your state, but in ours if someone like Malcolm is found dead of no apparent cause, no one knows him or his medical history, an autopsy is automatically done to rule out foul play or suicide. Or this from a CNN story about death by natural causes..
However, in the case of a younger person with no history of a medical condition, “an autopsy becomes a much more critical part of the process. Young people don’t just die suddenly,” Fowler said.
That would be Malcolm, not saying that heart attack etc cannot be ruled out, but I'd think there would have been an autopsy.
There isn't an answer as to what the physical findings are for a death by WCV..