As it stands it is better to go into battle with 3 revive scrolls than the single miracle scroll that you can carry, which should not be the case, because miracle scrolls are higher level. The reason I say this is because with the miracle scroll, you want to maximize its potential, so you wait till most of your heroes are dead before using it, but after using it, your team is all low health and basically done for anyways. With the revive scrolls you can use them as soon as a single hero dies without any penalty, up to 3 times.
So my proposition is to either up the amount of miracle scrolls you can carry, or make it so it also heals your heroes that are still alive. Maybe like 200 hp or something. Just enough that your party isn’t barely clinging to life after using the one miracle scroll you have. Seeing as its the last item you unlock, it shouldnt be one of the worst items to bring with you