There is no only "engine" or only "artist". Artist does the rigging/skinning and makes animation clips which are then used by the engine to process further. There may be IK solver work done on engine side, clip blending, attaching objects to bones, adding restrictions, ragdolling and so on.
Look for "inverse kinematics lookat" to find some read about this topic. Just to confirm I understand what you're trying to achieve correctly, you want to do something like this: