I really wish someone had the answers about pet scaling and what they inherit from your character, But i'm not sure the dev's have the answer

They do not scale with anything other than skill level. They also have half a wheel in the passive tree dedicated to pets. So they get something around 50% increased damage, 50%life, 85% dmg reduction.

I guess that explains why pets are so incredibly weak. Pet builds need to do way more DPS in order to be competitive, especially if you consider that they don't provide life leech and you have less control over where the damage is dealt.

So i currently run a warrior/summoner with infinity blade and it seems to work very nicely, im lvl 60 and going smooth
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I use only the golem 3 times (duplicated) on warrior shadow with the infinity blades (who gives buff dmg to allys rune)

At least there is one unique item, dedicated to minions
Hopefully later on in the game development, they will add more Rare / Legendary / Unique gear, that scales with minion

https://imgur.com/a/C6UtoZl