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I say this because Galliard gets beat up in every fight without fail,

Many of them weren't comedic however.
Clearly someone needed to take over the Jaw Titan from Ymir, and Porco's primary role as a character was that, and the first thing that was introduced about him as a character was his strained professional relationship with Reiner, whom he does not consider worthy of the Amored Titan.
Furthermore, he serves an initial important role as one of the few warriors who never set foot on Paradis and experiences the determination of the scouts first hand. The Battle of Liberio was purposefully mostly set from the other side and Porco's perspective serves to show the normal protagonists look. He has never experienced mere mortal men charging at a titan headstrong to kill it. The scene that shows the fear in his eyes as he first hand experiences how galvanized the scouts are after having faced so much was very pivotal.

Galliard and the war hammer proceeds to get beat up by Eren,

No, the Warhammer initially beat Eren until the help of Mikasa, and Porco managed to land a sneak attack and was almost able to consume Eren and take the Founder if not for Levi's interference who cut his jaw muscles at the last moment.

This happens virtually every fight that Galliard is involved in

Actually no. Gallard has been involved in three fights: the first was against the mid-allied forces where he saved Reiner and was instrumental in achieving victory for Marley, the two battles with Paradis were hard-fought losses that were very close with both sides about to win at multiple points and most of the titans on both sides battered.
you do realize he also almost eats Eren at one point right, quite frankly of most of the titans he gets closest to finishing eren of,  only the swift cut of one of his jaw muscles saved him (which shouldn't have stopped him eating since a jaw has muscles on both sides) >

Indeed that was close but what else would we expect from a titan whose name is dubbed the "jaw" titan and he sneaks up on Eren behind his back? Honestly, the fact that he wasn't successful in eating Eren really just proves my point of how incompetent he is. If your jaw is already on your enemy's neck, why would you wait to bite down? A competent jaw titan would have been able to bite Erens neck the moment he made contact, and the fact that Galliard didn't do that really proves to me that he is just a joke. And right after the sneak attack, in the real fight face to face, he proceeds to act as Erens punching bag.