That would still leave us with up to 240% Boss Damage/IED from familiars in a game balanced around having none
I really, really like your take, I just think they should be nerfed to the ground and be something you can work on slowly on your way to end game.
Then getting a second line would be part of late game optimization rather than a must-have early game item that doubles your damage
For healing, I think you didn't mean for Unique familiars to heal a "small amount" since that was already listed for epic. Pushing "Large" to legendary is fine if we can still stack healing.
The rest of the junk lines are there as filler so players need to reroll. We have them everywhere else in the game unfortunately and I don't see Nexon getting rid of a way to make us farm more or spend money.