Driven by hatred, Yale was attacking non-stop the birdman ancestor.
Yale's power had increased enough to put the birdman ancestor in a situation where he couldn't lower his guard, but since Yale wasn't calm minded, he couldn't use his strength to its max potential.
Due to the fact that Swordmad and Yale had killed a total of eight Law Masters in a few seconds, the army's power had been diminished, and Ronragruk's group was managing to tie them down, but since all of them had been battling at a disadvantage for so long, they were far more tired than their opponents.
Moreover, the birdman ancestor had already recovered enough power to battle seriously as a Law God, so there was no way Yale could divert his attention to attack the few remaining members of the army.
Ronragruk and the three Law Masters weren't strong enough to divert their attention while battling against nine Law Masters, so the rest of them needed to fight with the army remains.