I actually really like Camille's Personality and her Theme but I absolutely hate playing against her.
Her E removes punishment for misspositioning.
Her R is just an excuse if she misses everything, basically forcing you to fight her even if you have no chance because of how well designed her Q is.
As for Rek'Sai, she's got a lot of issues in a lot of areas and it would be best to go over what she is suppose to be.
A Diver? A Bursty Fighter? An Assassin? A Tanky Fighter?
Because she's got a kit that supports tiny bits of all of the 4 above and doesn't have one clear way of playing.
She needs a better Passive for starters.