Liquiir was off-guard. That shit doesn't mean anything. He even still managed to block it from point-blank range, despite it piercing him (which I would think a godly arrow would do). Him and Heles were equally fucked against Mosco from what I saw – he was grabbed and she was stuck in a tractor beam or some shit.
I think Iwne, Rumoosh, and Sidra were portrayed as the weakest, being the first ones we visibly see go down before the Grand Priest ended it. Belmod was likely playing a trick to avoid battle since after Liquiir's retaliation, we don't see jack shit from him until the battle has ended.