If you're spamming blood vials faster than you're farming them, it's a none-too-subtle message that you're struggling. Considering the game is only going to get harder, maybe you should take the hint and try levelling up elsewhere.
It would be a design flaw only if you didn't have that option.
Let's say you're stuck on gascone (something that plenty of beanies relate to.
You've already killed cleric beast and gone literally everywhere you can go.
In that situation levelling up will only get you so far, and the farming forces you away from the boss and slowing down your process of getting good enough to beat him.