Elladan is absolutely terrified, having lost his elven abilities he's hugely outclassed in this entire fight. But he's a soldier at heart and Dean's crash course on weapons was enough for his quick mind to learn. He lacks the finesse of people who have used these types of weapon their whole lives, but does what he can where he can.
He's not on the front lines, leaving that to people better suited for it. He doesn't get hurt, but would turn his attention to those wounded on the battlefield. While he lacks much of his father's skill at healing, he knows enough to stabilize some of the hurt people until they can be brought to actual doctors who can patch them up.