I am trying to use CoF to get additional gear, but I have noticed that the requirements-to-rewards ratio on many are completely out of whack.
For example, one Prophecy will require 3 Exiled Mage deaths with no conditions and will reward 4x unique weapons, and another Prophecy will require 1 Lagon death on 220 Corruption and will reward 2x unique weapons.
Why would anyone ever take the latter Prophecy over the former? 
Some players may be farming Lagon for other reasons anyway. For them, a Lagon prophecy would be free loot.
But there are Prophecies like āDeath of Boss x 1, no condition, 4x unique weaponsā as a comparison.
Whatever Prophecy you get where it requires a specific boss or a high amount of Corruption, thereās always a version at some point that requires a generic boss, or fewer boss kills or no Corruption, and with the same or more rewards.
In other words, the rewards of Prophecies do not appear to scale with their difficulty / tedium.
It does seem like the rewards are random and have nothing to do with the requirements.
They do have slightly different favor costs so I guess when it becomes a problem but I personally donāt have much of a problem with lack of favor besides the very first char but yes, the rewards are so random. And sometimes, itās just conveniency