Hang on, Hex is doing double damage when you’re wet? Even double damage for lightning when wet seems OP, maybe disadvantage on your save would be more reasonable.
Hex gets doubled on a crit since it is a die roll. It does not get doubled on wet characters. Regardless, I forgot witch bolt is channeled, so you cannot combine the two anyway.
Witch bolt, though, is basically quadruple damage on a wet target on crit -- wet makes them vulnerable, then the crit is double of the vulnerable amount. Super powerful.