The module tells the DM to "Roll dice behind the screen and frown.” That is meant to imply to the players that the monster succeeded on some kind of secret saving throw, suggesting that it might fail on a future attempt (even with the same roll from the players).I'm not sure how the players wouldn't know what happened. If I attempt an action and it fails, but trying it a second time works (with the same dice rolls,) that is strange.
How is the player prompted to try again after getting the feedback that the first attempt fails?
Still, if the module writers really wanted this to work, the smart thing would have been to provide the DM with some text to explain what's going on. Or, even better, to build the explanation into the story.
I don't disagree that those are more elegant and effective ways of handling the situation. Nor am I saying you're wrong to dislike this module's approach. I was really just trying to get to the bottom of what exactly bothered you about it.If the story needs more than one attack for the pacing, why not construct the encounter to need more than one attack? Either say that two items are needed (as I mentioned previously,) or you need to use the item twice to fully defeat the target (perhaps the first attack induces a weakened state, and the second is the killing blow).
Am I right in guessing you're the sort of player who also dislikes Quantum Ogres? Because this strikes me as a similar situation.