If you have say 75% find item, then it's the equivalent of killing it 1.75 time.
It does not ignore the 'noDrop' like it normally does on other mobs, but still, nearly doubling your herald's chance to drop a sunder is considerable.
At least worth using on herald lvl 4 & 5.
If your question is "is it worth farming heralds as a solo horker barb", then your density destroying capacities are very poor compared to S tier builds.
Horker is a nice elite sniper but far from the best at spawning heralds.
But it would be worth it having a horker following all herald kills while multiple people farm full terrorized games, as a team or with loaders.
Not everyone wants to run d2 games like a WoW raid. Playing p1 and horking Harold’s is #1 for p1 casual play.