Conceptually, I'm fine with the artillerist's turrets. They are just weak to the level of pointlessness. Just buff them a bit.
If you deleted the alchemist's homunculus you are left with an extremely weak class all round. It's a spellcaster who gains spells at half the rate of other spellcasters. I would leave it alone since a complete reworking would prevent the release of the class anytime soon.
The Archivist, you would have to design dungeons so the party can't camp in a safe place whist the invulnerable artificial mind explores and slowly kills anything that can't run away. Personally, as it is, I would just ban the subclass. I don't like the concept anyway, but I guess making the AM vulnerable to Dispel Magic and force damage would help.