Questions regarding Break Morale, Blindside and Viper

The tooltip for Break Morale says “Disrupt target’s skills for x seconds”. Is this supposed to work for heroes and bosses as well? Because when I cast Break Morale, mobs have no issues casting whatever they want, raising auras and whatnot.

Blindside reduces target’s DA. Does this cumulate? So, if a fight takes longer and I pull off multiple Blitzes, will my target’s DA be lowered multiple times?

Regarding Viper… The final node gives 20% reduced target’s Elemental Resistance for 3 seconds. That’s the stackable reduction, right?

Bosses are immune to CC, including Skill Disruption. Some heroes and even trash mobs are also immune or highly resistant to it.
DA reduction acts just like resist reduction, “-X DA” stacks and “X reduced DA doesnt”. And debuffs from SAME skills (2x CoF, etc) never stack.

Resistance reduction from Viper also doesnt stack with similar effects (like, Mindwarp, etc)

Thank you very much!
So I guess I better get rid of Break Morale, it doesn’t make too much sense if it won’t work on those mobs where it would be desirable.

Players use Break Morale only to reduce enemy’s physical resist. If you dont deal physical damage, you dont need it.

I like using it against those cold crabs in ugdenbog and outside sewars in malmouth, they can’t spit cold on your once you war cry them.