[Essence] Remnant of Corruption usefulness

I've used Remnant of Corruption a lot, but it seems to me that its better to crack imprisoned monsters as is:
I've used the Remnant on monsters with 2-3 shreaking or 5 essences with various tiers, including shreaking.
What I got from using them is complete trash: it seems only to choose the weakest tier and substitute it against all other ones.
In this league I have never seen a Remnant to upgrade tiers or add a new one or release a monster.
Is Essence mechanic broken or what?