I was thinking of a hindrance for all effigies: when the thing they copied is destroyed, so are they. Also, they wouldn't necessarily be able to copy everything perfectly. They would not be able to copy mage class only spells. This is also another reason why it might be important to have position control. Also, the trait "legendary" cannot be copied, although some effigies might have the trait legendary already, so a legendary effigy can copy another legendary spell that shares type and level with it. They would both stay in play because effigies would not copy names. Also, I'm thinking effigies can only copy conjurations, creatures, and revealed enchantments or conjurations attached to a copied creature or conjuration. So they cannot copy attacks, incantations, equipment, zone enchantments, or any enchantment that isn't already revealed. I'm also wondering if legendary effigies should also have the epic trait?
And I think you're right, Darth. I was worried too much about the Sympath's mimic ability being OP that I went overboard on nerfing it in the post. But considering all these other hindrances, I think you're right that it's probably better as mana-free and occurring during the first upkeep.