I feel like the Circle of Spores is trying to go in several different directions - is it trying to be a melee warrior? a zombie master? an AoE blaster? - and it needs a bit more focus.So, with that in mind... I would replace its features with something like the following. (Don't get too hung up on the damage numbers or ability ranges, they're just off the cuff. They'd need to be playtested and adjusted for balance.)
Halo of Spores (2nd level). You are surrounded by deadly spores that invade the wounds of your foes. When a hostile creature within 30 feet of you takes damage, if its remaining hit points are less than or equal to your proficiency bonus, it dies.
Symbiotic Entity (2nd level). As a bonus action, you can expend a use of your Wild Shape to have your spores attack any number of creatures you choose within 30 feet of you. Each must make a Constitution saving throw against your spell save DC. If it fails, it becomes infested for 1 minute.
As a bonus action on each of your subsequent turns, you can deal 1d6 necrotic damage to each creature you can see that you have infested. This damage increases to 2d6 at level 5, 3d6 at level 11, and 4d6 at level 17.
Fungal Infestation (6th level). As a reaction, when a beast or humanoid you have infested is reduced to 0 hit points, you can cause it to die and animate as a spore zombie. The spore zombie obeys your telepathic commands and acts immediately after your initiative. It dies after 1 hour, or whenever the number of spore zombies you control exceeds your proficiency bonus.
[Stats for spore zombie: Basically, it's got AC 8, 1 hit point, speed 20 feet. Its only action is Spore Burst, which also triggers when it's reduced to 0 hit points or dies; each creature within 5 feet of it must make a Con save. Those that fail become infested by you for 1 minute.]
Spreading Spores (10th level). Spore zombies you create have their speed increased to 40 feet, and the range of their Spore Burst ability increases to 15 feet.
Fungal Body (14th level). As an action, you can disperse your being into spores. Your body and carried equipment vanish, but you retain control over your spore zombies and can see through their eyes. Whenever one of their Spore Bursts is triggered, you can have your body and equipment re-form within 5 feet of that spore zombie. If at any point you have no spore zombies under your control, your body re-forms in its original location.
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