I can see that break moral has as part of the skill a modifier that says disrupt skill for X time.
What does that mean, that mobs can’t use their abilities? Does that work on bosses or do they have a resistance to it?
How effective is skill disruption as a combat skill?
Yep. They can’t use abilities. Bosses are usually immune to disruption. It’s not that great but it has its uses. You can disrupt casters like possessed mages and bloodsworn cultists and make them go melee on you or stop those fire zombies from exploding on death.
and also disrupt healers.