Henadic Theologian
Legend
While that is what they generally get used for, summoning creatures are extra hands for many, many more tasks.
And with concentration in play, only one spell should be active for a given player at a time. If they want to summon a horde instead of a single creature, the DM can either put their foot down, demand the player be quick with their turns or use mob/swarm rules for the summoned horde.
Actually the Lemure/Dretch/Larvae Swarms seem like a great inspiration for new Summon X spells, that mimic hordes.