The rock elemental is an amazing gatherer mostly for stone, but also gets some insane amounts of meat, and keeps it from getting spoiled for a good amount of time. Rock elementals also are one of the best defenses against dragons. The rock throw attack seeks the nearest target agains you to make the attack a little easier to make contact with target
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.