Snoop,
I'm not sure there is a strong link between pay and skills. I think it is clear that these pilots had no place in their respective seats but the question that is significant to me is how did they get to this position if that was the case.
I believe the check and training department has a lot to answer here as well as these poor souls.
As for the FO inexplicably switching off the ADIRU rotary selectors, it would be interesting to find out what the captain was thinking when he asked him to 'reset nav'