We only rode in fp line so I didn't see main loading for the line. Is there any chance one of the theaters was down for repair since they had so many problems and they just opened it back up?
I did FoP as standby at rope drop (make sure you are there early - if you are running behind, skip it as it will suck up your whole morning if you are behind the crowd). Afterwards, we had a 5-10 min wait for Na'vi River Journey via standby.
I also did FoP again later with FP+ - it is such an amazing ride, I'd highly recommend it.