Really cool objective. The fact that your score is how fast you can finish means that there’s lots of ways a player can flex their skills for the high score. I also like the risk element when you’re rolling the dice, knowing that healing is going to increase in cost if you mess-up before the boss fight. I also like that you can really ramp up risk by rolling multiple times. It’s a cool way to go about it.
I’d recommend making the dice roll animation not take up the whole screen though. I think the target audience for this style of game is someone who wants fast-paced gameplay so they can speedrun the boss. The animation is going to feel like it’s slowing them down and killing their momentum. I would definitely lean towards decisions that help reinforce a fast-paced state of gameplay for this game.
Cool concept. I’d keep this style of game in your back pocket if you ever want to make a bigger game in this style.