Guild Wars 2

How about introducing an NPC, called idk Bob the Collector or something, who will trade you the precursor of your choice if you trade him 1 weapon from each dungeon of same type.

For example, if you want Dawn, you would need to trade him 8 greatswords, one from each dungeon. You can make it so Bob can only be accessed after completing something difficult, or add a 100g surcharge for the transaction. Whatever need to make it a CHALLENGE. Not dumb luck as in the current system.

Also, make it (and Legendaries) account bound.

Legendaries should be the reward from hours of hard work and being able to play every aspect of the game, not something you can buy with gold you bought from illegal gold sellers.