Rather then nerfing the thralls damage and HP ect, why not simply restrict there gear.
To explain, prevent thralls from equipping legendary stuff, buff legendary stuff notably.
This way for normal mobs thralls and pets rule, for bossed they are ok, but also this gives a reason to get legendary stuff and allows players to really excel with legendary stuff.
Though some work might need to be done for PVP, like a flat damage reduction to hurting players that effects thralls and legendary gear ect or something (I don’t really do PVP)
But the point is that rather then nerfing thralls and pets (pets really don’t need nerfed at all anyhow) you could make legendary stuff relevant more and give a reason to actually run dungeons and kill bosses to get it, while also making player with them better then thralls who wouldn’t be allowed to have them.
Edit: fixing typo