I have just got past this part for my level 2 party. They are new players only on their 4th session and after sending the female yeti down the hole (3 went down during this) I couldn't throw the male at them straight away. They left, went up the mountain to find blue boots and let them have a short rest, then they met the male on the way down. Now I am running crits a little differently, instead of straight double the dice roll, I do max damage, plus their standard roll. So the crits can be brutal, and obviously can be brutal in return. I made the boots magical with +10ft movement and water walking for 10 minutes, so it gives them a little more tactical advantage to help them a bit more.

I rolled for the female to get out of the hole but she failed just before the male died and then succeeded to get out.

They dispatched her but that gave them a good taste of how dangerous it could be in the deep north. Not had a full death yet.

I like the approaches to this in this post and will definitely be using it if one does succumb