On multiple occasions, while having "Dáin, Lord of the Iron Hills" on the battlefield and with the Storied mechanic active, my opponents are still able to attack me without paying the tax. This happens regardless of the amount of mana open, even when tapped out before combat. The Storied mechanic itself seems to be working, as the symbol appears indicating that Storied is active once the conditions are initially met, and other Storied creatures work without issue such as "Bifur, Melodic Rider" who was on the battlefield at the same time and doubling triggers. The game seems to be failing to enforce the conditional check for his static ability.