He may look like a lazy hippy who can’t hold his own, but Terra is merely lulling you into a false sense of security. Terra is the creator of solidity. Without him nothing could take solid form. This leaves the poor guy pretty tired so he usually sleeps for a few millennia.
In battle though he puts immense emphasis on taking hits. He comes equipped with protection spells and increases the power of physical type cards and abilities. Terra wants to make sure he can just live though the damage he takes and crush his foes afterward. It might take him a little longer to win, but slow and steady wins the race, right?