He's not even superhuman.
Still human
On the contrary, he is more god than human. Gilgamesh was the original determinator, continuing on his quest to find eternal life even though mortals and immortals alike strove to stop him. Along with Enkidu, who didn't really do much, Gilgamesh built the walls of Uruk himself, though they were the largest walls ever built (at the time), as well and remained so for many years.
Gilgamesh captured
Humbaba, a giant raised by the sun, by punching him ONCE. No mere man could have done such a thing. In fact, the only one who could rival Gilgamesh's strength was specially made by the gods to be his equal.
Slaying the
Bull of Heaven was another of Gilgamesh's feats of might. Near the bottom of that text, you may read that Gilgamesh smote the bull (the bull being thrice the size of a normal one and many times stronger) with an axe (weighing seven [Babylonian]
talents, or 469 pounds.) so hard that it was smitten asunder and 'spattered like rain, spreading itself over the crops'. You'd have to be incredibly powerful to lift that, much less raise it over your head and smite a giant bull asunder!
This strength is only surpassed by his skill. Enkidu was created to be his equal in strength. As you can tell in the above paragraph, this was mighty indeed. However, Gilgamesh threw down Enkidu in a wrestling match with ease. Also, there were two man-scorpions guarding the entrance to the realm of the gods, who were always as strong as those who challenged them. These too he defeated, though outnumbered and matched. When crossing the Sea of Death that led into the realm of the gods, Gilgamesh
slew several giants who were made of stone, a rather unkillable material.
Endurance is also important in such a fight. Inside the realm of the gods, Utnapishtim (the only human to become immortal) tells Gilgamesh of a plant that can indefinitely extend his life, but it is at the bottom of the sea. Undeterred, Gilgamesh swims to the bottom of the sea, so deep that he sees no light, and has to fend off the beasts of the deep. He recovers the plant, and only fails in his quest because the gods sent a snake to steal the plant while he bathed.
Due to Gilgamesh's strength, skill, and endurance in combat, Terra's melee skills would result in her death. However, let us take a look at her 'magic' abilities... [NOTE: This is all based off of the information
here.]
Terra learns many healing spells, but these would run out before Gilgamesh's endurance ran out. Drain spells would also fall under this, because Gilgamesh would likely have more HP than Terra has Magic.
Gilgamesh is immune to her fire-based spells, as he is immune to fire. (In tablet 12 of the epic, he is not harmed by the fire that spurts out of the underworld at him when Enkidu's ghost leaps free.)
Poisona and Dispel would be useless against an opponent such as Gilgamesh, who doesn't use either poison or magic.
Resurrection spells don't work after you die.
Teleport would be more useful if this wasn't a fight to the
death, but a fight to the exit.
Gilgamesh's mighty strength would loan him a resistance to Gravity spells, thus rendering them less damaging.
Break (or Stone) would be somewhat useful, if not for the fact that it renders opponents
immune to damage. Also, it has terribly accuracy. (47% by my calculations) therefore, it'd be easy to dodge.
Holy could do some damage, but Gilgamesh's two-thirds-god would likely produce a resistance to that elemental type.
Ultima could probably deal quite a bit of damage, but probably not enough to kill someone who once kept fighting after bleeding a dozen gur (roughly 960 gallons) of blood, enough to almost cover the floor of the cave he was fighting in.
Now, off to this 'Esper' topic. Apparently, it can be used only once in combat, and for a set amount of time. I put forth that Gilgamesh can use his endurance to his advantage by running in cicrles until the effect wears off.