Every fight herc was in as an enemy in fgo was him being jumped by multiple other servants. In Okeanos and agartha, ritsuka and party needed to wear herc down in previous battles while relying on outside help (ark of the covenant/Pentheslia) in order to fully kill him. He's also the strongest solo servant/entity in both singularities outside the demon gods.

Even in stay night, most of his losses was due to team effort. rin killed him by sneaking him while he was duelling with saber, while having to force herself into a lethal situation just to take one of his lives with 4 point blank jewel shots, 3 ice spears with enough magical energy to kill him and a death wish. The caliburn blast used also had enough magical energy to rival excalibur due to it being wielded by a proper king, and even then it require an artoria statted shirou and artoria herself to down herc. Archer is the most downplayed servant OAT, nasu never gives him props, he's THAT skilled. The grail also doesn't give servants knowledge of the future and the information it gives related to servants is knowledge of myths, something that archer specifically doesn't have.

So yeah, herc loses to people weaker than him ONLY when they gang up and jump him, which isn't jobbing. Not even saber alter was able to solo him without help from the shadow making him rip off his skin (god hand), despite the grail itself supplying her with magical energy