So the stipulation about performing rituals requiring a dark die just means that a PC has to be willing to risk their mind or body in order to succeed. so rituals are inherently risky, which requires a roll, then you look at how you build the dice pool:
Take one light-colored die if the task is something you are skilled at because of your occupation, background, or training, or because you are taking advantage of a piece of equipment or the environment.
Take another light die for accepting a Devil’s Bargain from another player or the gm.
Add a dark-colored die if you are willing to risk your mind or body in order to succeed. You must include this die whenever you perform a ritual.
Very few premade occupations/backgrounds include a “rituals” skill, so the chance of a PC being skilled at it is low, which means they have to take a devil’s bargain if they don’t want to automatically take Ruin (since rolling only a dark die would necessarily make it also the highest die rolled) — and with only one light die, in that case, there’s a not bad chance that that dark die will still be higher; so that’s probable Ruin and a related side effect if not definite Ruin for no side effect.
I think it’s a value judgement, really…they seem very lethal to me, especially because, if a PC starts with three rituals, they also start with four ruin — that’s not much room for error!
Let me tag @jesseross, too, in case he has further/better advice *~