The snow slab story fits all the other evidence: there was a massive slide of ice that rolled over the tent and burring it.
the hikers that were not seriously injured cut themselves and quickly made their way down the hill to find some safety from further avalanches, but some where found just wearing underwear. those stayed put around a quickly made camp fire, which is why they also appeared 'tanned' as they stayed too close to the flames. it was a very windy-cold night.
The others tried to make their way back to camp; however, finding camp in a windy storm at night was hard and they failed. I think it was 2 had fallen into a ravine, and the rest died due to the elements.
Ironically, those in their underwear lived the longest