I designed the Screaming Mandrake to be sort of a mid-game ingredient. You’re meant to have a good stockpile of them by the time you reach the late game. I understand why it feels unfair right now, though, since we’re still in the early game and there’s no reliable way to obtain it aside from RNG.
I’ll try to add transmutation in the next update. Once players can create Screaming Mandrakes on their own, that will mark the transition into the mid-game phase. At that point, getting an extra mandrake from RNG drops won’t matter nearly as much as it does now.