If you’re primarily concerned with survivability and pure “tankiness” (where you’re the one doing most of the damage), then a tier 3 or 4 bearer thrall and enough authority to allow them to taunt. Armor rating has diminishing returns, so once you’re in epic heavy you get less bang for your buck there.
As far as pets go, they’re useful for carrying stuff around early game, and of course you may like how one looks cosmetically. Functionally though? Give them a hard pass. They’re worthless against anything but the most trivial enemies.