TPKs are Not Fun

A starter set for a roleplaying game can have many objectives, but among the most important, surely, is the need to draw players in, excite them, and leave them eager to play more. The Soulbound Starter Set, by contrast, makes me want to stuff its terribly unbalanced introductory adventure into a troggoth's maw. One combat encounter early in the adventure gives players a two-in-three chance of encountering either a spine-worm or multiple bore-beetles. In either case, the party is completely overmatched. Both creatures have attacks bearing the outrageous Rend trait (with attacks at 8D6, so you're looking at a 77% chance per attack for permanent armor damage), and both also have Mettle -- a game mechanic that (among other things) allows a character to make a second attack on their turn. Maybe I'm truly not understanding the math of the game, but I can't see how you can avoid a TPK unless you have a full party of five heroes, all at full strength, and you get really lucky. How is this fun?!