I think having a dietician working with a doctor's office, say, a family practice office, would be a huge asset. Many long-term conditions can benefit from a change in diet, and I've seen exactly one doctor who will give more than 5 seconds of advice on the subject. (That's the one I go to. He has the same personality in the hospital as in his office too!)
The reason I wouldn't advocate seeing a "nutritionist" independently is that, precisely because they can't order lab work, nobody is getting a complete picture. Any RN can examine a person, as in, they can look at someone and be in the middle of a mental assessment, that's just a skill. I don't claim to do a complete physical on anyone, however. If I'm not mistaken, my personal doctor defines that as: you have the lab work sitting in front of you. You had your pap smear done. (by his nurse practitioner) You brought me 3 months worth of blood pressure readings, nice. Physical exam in office, taking all that stuff into account and handing out either recommendations or a diagnosis, or a "see me next year."
It seems to me this RN maybe is a NP, or maybe isn't, who's to say... but I'd recommend using a NP in conjunction with your physician, 'cause I'm spoiled on my family doctor and think people should just have it that good.