I think a token system would be better, like what they've done with the EX modes. I tank in our FC coil group, 3 drops for my dragoon but none for my tank. That's not really fair to all the people who have been grinding for certain pieces for months, but with a revised system they could actually get what they've been looking for.

If the intention for RNG is to make people play over and over again, then just set the amount of tokens earned appropriately. IE, if the intended success rate is 20%, then (earning 1 token per turn, excl turn 3, maybe 2 tokens for turn 5) have each item cost 5 tokens.

It is nice if you get a couple drops in a row, but so not nice grinding months for no drops. Need more balance.