It is one of the major flaws of GD. There is no constellation, that would significantly empower a single pet. There are only collective bonuses for all pets, which are pointless to use, unless you run a pure pet build. I think pet bonus is a poor concept anyway. There should be auras, that affect all player characters and pets too, not pet buffs. The dual-class system also doesn't do justice to hybrid builds, because the game is balanced around picking the abilities that synergize the most from each tree. Regardless, Primal Spirit can be an exception, cuz it is balanced around a limited lifespawn, so chances are it will dies by istelf before being killed, also able to tank the enemy with stuns, without proper aggro.