He focuses to make the barrier soft enough on their side for Tidus' attacks to go through, it's tricky but he's determined to help out Tidus as much as he can.

Lightning comes down and the dogs run barking. Romeo nodded at Tidus. "Line!" Sending an attack through his shield he struck the ground near one of the dogs that he ran forwards again, sending it skittering backwards.

"I think we are scaring them off!"