Then you have misunderstood the purpose of the Deadly Sphere Staff. The purpose of the Deadly Sphere Staff is not to summon a horde of them, but rather to deal instant 100 damage in a line towards the closest or marked enemy every resummon.If I want an alternative to Blade/Sanguine there's Raven Staff or Desert Tiger Staff, two other summons that are way better than Deadly Sphere Staff.
It also falls under the category of items used to kill mobs above your event grinder, which includes Optic Staff and Pirate Staff. No big deal if you don't get it, though.
The thing about Deadly Sphere Staff is that you don't really have to go out of your way to farm for what is essentially nonessential for the run. If you get a Solar Eclipse, it's a nice free Deadly Sphere staff. If you don't get one, no biggie. Just go straight for Cultist and Stardust Dragon. Pumpkin Moon is honestly overrated anyway (though you can skip Moon Lord to go farm a Pumpkin Moon with your swanky new Stardust Dragon staff if you don't feel comfortable with killing ML without Papyrus/Necromantic)
Side note: It's also the only summon staff that can be used against Enraged Fishron in a minecart cheese arena, so if that's how you roll you will need that staff.