If you have a card from a raid, you should only be allowed to roll greed

[Airget]

It's an evil system, but it's there to get people to do said content more than they normally would. Now I think there is a way to exploit ones vanity with these cards but I don't think people are going to like it. Foil Cards. Let's say you can only Need the card on a weekly basis and greed the rest of the week. However the cards which drop in this manner now have an RNG chance of being a foil/shiney card when used. You would have a group of people who do said content, fight over the weekly need, and then attempt to greed the rest of the week if they really wanted the "rare version" of the card while not affecting it's purpose in being there. To get people to do the content more than they would.

[Zojha]

It's an evil system, but it's there to get people to do said content more than they normally would.

That can be achieved with several systems, tho'.

If you have a 10% chance to get an item or you have to get 10 completion tokens from that content, the average amount of runs to get it will be close to identical. RNG only adds a very minimal amount of extra runs on average because outliers are open ended.
Likewise, having a 10% chance for an item to drop and having 4 people roll on it is roughly equivalent to a 2,5% chance for the item to just drop into your inventory. Which is equivalent to needing 40 completion tokens. On average of course.

You can freely convert between personalized loot systems, open loot systems and token systems without compromising the function of the loot - to make you re-run content. RNG systems in general have the advantage that they allow for instant gratification despite high average run numbers (and thus, function like a cross-subsidy from unlucky players to lucky players). Token systems equalize the amount of runs and don't allow for instant gratification.