Given the close proximity of such a device wouldn’t there be scorch marks and damage to soft tissue? Also, evidence in the snow of the device, metal fragments etc?
What if the blast came from much further away?
Well the luxury you have with ball lightning is that as no one knows how it explodes (or even why?) it could be made to fit any profile, very local but subsonic and with no flash burns. If you went up in a microlight and were next to a lightning bolt the resultant thunder clap would be powerful but subsonic?
The injury profile is that two people got it very bad, others (like Rustem) much less (which assumes of course it's from the same event). Presumably a more distant, more powerful blast would be more equal in it's damage? Also there would have to be tree damage?
Personally i think Lyudmila's one rib pushed into the heart is difficult to explain from a blast? Much more easy to explain as impact? Unless the blast is throwing her against something pointed.
I'm getting into the idea that they fell into the ravine perhaps down a snowbank that focused the landing point. I've always argued that this is completely against the injury profile (no limb injuries) but if they fell without conscious control then it starts to make sense. Imagine being on top of a one storey building like a bungalow with the roof covered in ice with a group of people who follow you down one after the other. Now imagine everyone is blindfolded so they can't react. Now you slide down the roof and land on a girl's chest. Then someone lands on you. The girl and you are in say snow a metre deep. Impacts to the arms and legs just push the limb deeper into the snow but the torso doesn't move down so easily and the head is strongly attached to the torso (unlike the limbs which can also rotate). So the first ones down the slide receive the worst injuries with the last ones just picking up bruises.
The ravine could have been very dark.... and as previously argued at least one nitrogen oxide intoxicates and heavier than air gases would collect in the ravine. Also warm gases including air could make the snow unstable causing a group of people walking single file to fall as a group one after the other perhaps..