First off, the attack boost is 3x, which is stronger than I expected. But the main point isn't that—it's the unique "Armor Break" mechanic.

​Once you take damage, you lose the attack boost, and your HP is cut in half. This state can't be cured until you move on to the next stage. However, because this breakage happens instead of taking damage rather than on top of it, it can essentially be seen as an HP shield that absorbs any hit and refreshes every stage. Plus, this effect even works against instant-death attacks.

​That's why it's actually much tougher than you'd think.