This is my problem with it.
Warlocks should have their own system like, just off the top of my head:
1)Cellar of the Slaughtered Lamb and the Horde equivalent (sorry horde folks, haven’t played that side yet) are revamped with a summoning circle in the center and a grimoire floating just outside of it.
2)Character stands in front of the grimoire and player clicks on it. A list of demons pop up, the selection based on character level. All grunts and no taller than any character, no elites. (Incubuses are an option.)
3)Player clicks on the demon they want and it appears in the summoning circle. The character enters the circle and must prove themselves in combat with the demon for the demon to treat with them.
4)When character successfully drives them to surrendering, a contract appears in the air. RNG kicks in for the price (mana, gold, first born, the usual!), character pays the price and the player has a new cosmetic for one of the slot.
5)In order to get the old one back, they must go thru the same thing again. Can only hold contracts with up to five demons at a time, depending on level. (Why five? It just seems more mystical than four .)