Rock elementals are extremely tough to kill or knockout. Over encumbering them inside or around your base and setting them to aggressive allows them to defend your base with their rock throw attack without being kited away by enemies.
Takes 10% from everything but explosives and does not take damage from elemental attacks like fire,poison,lightning. A tamed level one rock elemtal has 3000 health a wild one has 20000. So if your enemy does not posses explosives,mek modules, cannons then your rock elemental technically has 30000 health plus the Armour on the saddle. So a tamed rock elemental has proven to be more powerful in combat then a tamed giga I dont know too much about damage .