Well to be honest I think you both have a few valid points.
When you look at how CoF works and the rewards that you get for clearing a stage 2 things become clear.
1: The gold reward is fairly decent compared your player level.
2: The item rewards are completely random and have a huge variance.
It is possible to get a single grey item from stage 14 and get a random hero card from stage 3, this also means that the rewards are not really on par with the level of content that you're beating.
I personally think that CoF needs an overhaul, the item rewards should have less variance built into them, I do however think that the gold that is awarded is fairly decent, however at level 100 it vaporises fast
As an example I decdided to calculate the gold rewards from 1 run today and came out to be 1.775.500 million gold (rounded down) for a level 100 that is gone very fast, however it is still a decent amount.
When it comes to the item rewards I think it is safe to say that we could use a better system. The system should take player level into account and then give out rewards based on that. Now I don't need/want cof to be givig out purples/oranges left and right. But I think it would not hurt for the possibility to discover fragments.
It is much more satisfying to see 3 fragments for let's say a Lost epic then it is to see a random blue item. Or when you're around level 64 orso to see a few fragments for a sage wand pop up from a random stage.
But most people see cof as "free" gold and vip10 basicly add 3.5m per day to their accounts and they're happy with that and everything else is considered icing on the cake.
I wouldn't say that changing CoF should be a huge priority though.