Raoul, Don't be frustrated. NCL has been challenged by the gratuity issue. They have tried all kinds of things to change the way gratuities impact performance. As an example, Joanie was on the Pride of Aloha recently when the policy was in transition.
If she left a gratuity (on her onboard account) with her server, then the server got a small portion of it, while the bartender got the lion's share. If she wanted the server to get it, she would have had to tip in cash.
Many people on the cruise were confused by the policy and it seemed to have changed during the cruise.
My advice? Tip early and in cash to get the attention of servers you want to perform for you during the cruise. Don't worry about the ship's policies, just identify those that may be important to your satisfaction with the cruise and take care of them early.
Just my opinion.