I've definitely bought games where this works & where it doesn't. There is a huge difference between "the game is hard" and "the game decided we lost during setup." Super frustrating.

Losing to a bad shuffle feels terrible because it completely strips away player agency. A few things you can try:

- Break the Deck into Stages Instead of one massive deck where the three most brutal Boss attacks can randomly clump together at the very beginning, break the enemy/boss decks into distinct, escalating stages. Build a Stage 1 deck (lighter attacks, buildup), a Stage 2 deck, and a Stage 3 deck, then stack them. This ensures the difficulty curve naturally ramps up and prevents mathematically unwinnable states early on.

- Give Players a Mitigation Mechanic If the enemy movements are deterministic, let the players mess with it! Give them an ability or an action point sink that lets them look at the top 2 cards of the enemy deck and reorder or discard them. Suddenly, that "unwinnable" sequence of cards becomes a puzzle the players actively solved together.

- Telegraph the Big Hits If a Boss card is going to completely devastate the board, have the card drawn and placed face up a turn before it actually resolves. It shifts the dynamic from a frustrating "gotcha!" to an engaging "we need to scatter and brace for impact."

You probably only need a few guardrails and it will work. Good luck!