Sacrificial Pit – how to use it correctly?

The number of Terran Enforcers is small, so even +1 Fury makes a noticeable difference....

In a long game, Furies are quickly eliminated due to their low hit points, and increasing their production requires eliminating a large number of enemies.
It's better to use mentorship to develop secondary Warlock heroes and have them engage neutral creatures and weaken the enemy army, rather than simply eliminating the neutral creatures themselves.