Couple of things that i think are bad about devourer and should be fixed

First of all devourer is an item for late game damage dealer junglers the item is adjusted to work mainly in that way

First thing is that devourer deals magic damage

the effect of this is that many champions who use it can forgo an item like last whisper ... this gimps the counter itemization to frozen heart truly since nor thornmail nor randuins will do much for you

and if you decide to build magic resistance you get rekt by physical damage

carry type champions shouldn't be free from itemizing penetration

Second thing ... is the devourer snowball effect sated devourer amplifies a kit ... so said kit is stronger in late game ... this makes it worth for said jungler to not gank as often as other junglers would try

but then there is the fact that devourer itself when obtained early in the game can prove to be a good item there are rare cases where devourer jungler snowballs which makes riven seem weak in comparison

and this early snowball usually due to some gold boost form a successful gank or other occurrence ... increases said junglers map control and usually guarantees him to get sated very early into the game which ends in unstoppable steamroll which enemy team cant counter in any way even if they deploy any available counterplay correctly due to the difference in sheer power

The item itself is fine ... but there are some cases where it doesn't behave the way it is meant to -a jungler who throws away early pressure to get the late game pressure ... shouldn't be able to obtain both -and a carry who builds offense without any penetration ... shouldn't be able to effectively deal with a target who builds defensive itemization

at some point even vayne's usually take a last whisper .. since it might take for them over 20 autos to deal with a tank