Why would the Uber Morlocks need so many? Is it possible that, unlike the earlier version of the film, the Uber Morlocks were afraid of the Eloi and so needed an army? But that is sort of contradicted by the Uber's statement that the hunters would kill all the Eloi if not kept under control.
In the scene where the hunters arrive in the village, the Eloi do offer some resistance to the Morlocks. Going mob-handed seems to actively discourage the Eloi from using any violence (they resort to running and hiding, mostly) and prevents the Morlocks from needing to use deadly force to protect themselves.
The Eloi scramble desperately to protect their children -- the Morlocks are brutal -- great claws slamming Eloi aside or snatching them up -- nets swinging -- the Eloi never really resist -- once they are captured they allow the Morlocks to pull them away --
Having sufficient numbers also allows the Morlocks to perform an encircling maneuver, appearing in front of the Eloi as they're making for their boats and preventing them from escaping (which in turn allows them to capture their specific targets, apparently the fastest and smartest of the Eloi)
Everywhere around them the Morlocks are netting Eloi and dragging them away -- But it is not random. The Morlocks seem to target particular Eloi.
As to why the Uber-Morlocks need quite so many Morlocks period, the answer is that they use them as physical labour to operate the machinery that keeps their subterranean world ticking along.
Machines. Towering, sweating, industrial. A network of enormous pipes and electrical cables and air channels like the circulator system of a body that twist off in every direction. A sweatshop Hell. A mechanized Dante's Inferno of wood and leather and steel.
And the Morlocks are working. All the machines are powered by the brute strength of the Morlocks alone. They labor among the hellish machines -- slowly turning great wheels and pulling at enormous bellows and hauling ropes and grinding levers. They are nightmare figures of a Bosch painting.