I think the best option would be to guarantee a Totem/Nut to everyone in the party every win and have 1 or 2 weapons drop 100% go random in the pockets of two lucky guys.

This way it could take 40 to 70 wins to get all weapons. And 40/70 wins is enough for anyone to be fluent with the battle.

Yes, this is the key point for me: only people who know the fight so well they rarely make mistakes should be 7/7. On the other hand, once someone knows the fight very well, he will feel stupid doing it again and again and get frustrated.

So it should balanced.