Yes, I know one item is op, and the other is nerfed, but in my experience, I find it hard to farm devourer when my team is either begging for ganks or dying in lane. There are also times where I feel I should be more tanky. Is it situational?
Devourer should be used in every situation. You can buy extra tankyness, you can buy the Sunfire passive, but you can never buy the Sated passive outside of getting Sated. Even if your lanes are doing badly, you can still wait for late game and wreck everyone with Sated.
Devourer.
Its cheaper to get devourer then go full tank than it is to get cinderhulk and buy more damage.
Devourer has AS resets for [Q] and [R]'s Fury production. Synergizes extremely well with your passive on-hits. Cinderhulk focuses on living as long as possible to take advantage of your AoE.
Devourer is in almost always more preferable for its damage output.
As Shyvana, gank if you have ult, farm if you don't. That's how a lot of Devourer junglers work, like 
(moderate ganks without ult) 
(moderate ganks without ult) 
(poor ganks without ult) 
(poor ganks without ult) etc.
Only one devourer jungler that I can think of has really strong non-ultimate ganks, 
. Other than him, you should be using you time when ult is on cooldown (or needs more fury for Shyv) to power clear camps and take dragons and scuttles. that's how you keep your team happy while still stacking at a remarkable pace.
