I don't care what RDM is actually like, there is literally no way to mess it up as long as they stick to the basic idea of the class, a jack or all trade style. It's basically what makes RDM an RDM. Be kinda hard for them to mess it up, even for Square.
As for Sam, that is another story. I see it just being a Dark style with more focus on the sword then the dark magic. I don's see it being like the Sam we remember in FFXI. In my opinion THAT is the Job we need to worry about.