From a rather iconic threat analysis back in the day:
e) Demo Shout ftl. Demoralising shout does one sixth the threat of a sunder. Even spammed in defensive stance with defiance, you’re doing no more threat than 42dps on each mob. Besides picking up whelps in Onyxia and tanking panthers in the Panther boss encounter in ZG, i can’t see a compelling reason to use this.
And another from a reddit post :
Demoralizing shout = situational. When Demoralizing Shout is working correctly (read: not splitting threat between targets), it does 1/6 of the threat of one Sunder Armor per mob. Even with Defensive stance + Defiance, it does not generate enough threat by itself for you to out-pace healing aggro when tanking multiple mobs. In general, individually Sundering mobs (via tabbing) + Battle Shout + Cleave/Whirlwind will be of more use to you than spamming Demoralizing Shout.
The amount of people misremembering and mixing up battle shout and demo shout is staggering. BATTLE SHOUT was used to cheese nef and twin emps. Demo was never good for consistent aoe threat.
If Blizzard comes back and says this is working as intended I’ve lost complete faith. I can almost guarantee demo shout instead of dividing threat per mob is full threat for each mob or even giving a bonus for each mob, which is not how it functioned at all.