Not trying to be argumentative here, just pointing out that Darkest Dungeon isn't a very good comparison.
What do you learn from one-shots? A lot, potentially.
- Can you defend against the attack? How? Try Dodge and Guard and observe the damage difference, if any.
- Is it simply a matter of stats? If the attack doesn't overkill you by hundreds of thousands of points of damage, you're probably just not strong enough yet. If it does, it's a surefire indicator there's a "trick" to the attack (if it's a charge, break the charge; it might be a resist-able element; maybe it's always used on a certain turn).
The following applies to all games, not just Black Souls. Frustration is always the fault of the game designer, but you have to remember that it might be by design (Getting Over It is a prime example of a "game" built on player frustration and the sense of accomplishment/bragging rights that comes from success). However, brute-forcing a problem (Requiem/Grit spam for example) is a sign that either A. you, the player, are simply bad at the game or have failed to grasp some key element of the problem, or B. the game designer has failed to communicate the proper solution, often a mixture of both.
You're right, Dark Souls as a series generally doesn't have any bosses that one-shot you (unless the attack has a clear tell or easily avoided/dealt with). Black Souls is the same. The difference between Dark Souls and Black Souls is that Black Souls does a terrible job of explaining all your options. Oh, and it's a game with even more broken setups than anything that has ever been available in Dark Souls.
