The term hard and challenging can be taken in multiple ways

It could mean the fight is rediculously hard and you can earn it that way
or it could mean it takes so long its a pain in the ass and its hard in that way

there are several ways this can be looked at.

but if you have a solid group, who does this regularly, and makes sure it stays at rank 2, all 8 of you can easily have enough within a month of work, the fact that so many have 3+ already after a single week proves that.

its not gonna be fast and easy to obtain, thats all we know right now