[X] Have everyone attack at once.
-[X] no, really, everyone
--[X] when you said everyone, did you stutter? You meant literally every person in camp. All at once.
If we don't gather literally the entire camp that's alright, but we should be able to get at more than we already have. If people have a problem with the fact that there aren't enough pieces to go around, they can either challenge it on their own and fail, wait until we've taken them all and fail, or join us in taking them and have an actual chance of getting a piece after.
I'm assuming that Pyrrha knows of at least a few stories of bitter enemies standing together against the Grimm, so this would be a good time to us that for inspiration.
This can be seen like the bell test in Naruto. You have no shot at winning on your own*, but if you band together you just might pull it off. You could work with no more people than there are bells to go around, but that hurts your chances of getting the bells in the first place. In the bell test, no matter how you look at it, a 2 out of 3 chance to pass is far better than having no chance at all.
*unless you're an overpowered OOC problem, but that's usually in bad fanfics (or humor focused ones)