My experience has been the casino workers are friendly enough but not the most knowledgable of the games. Some of them are, but I am amazed at the number who are not. I'm assuming (bad idea maybe) that most passengers in the casino are casual gamblers and are not terribly committed to the action or the intricacies of the skill games.
Craps and blackjack dealers have been unable to correctly guide the games and keep the payouts accurate. On one Carnival ship I had to instruct the craps dealer what the proper payout was and on more than one occasion return chips to her which I was not entitled to. Most people would've taken the chips and said nothing but I don't like being dishonest in any manner.
I don't think they go through the same training regimen land based casino operators do. I may be wrong, but I've never seen the errors committed on land that I've seen on sea.