I am no expert on dandruff, but I am getting amazing results from going shampoo-less ("no-poo") and washing my hair with baking soda and rinsing with apple cider vinegar. There are a number of threads on here about it. Before the no-poo, I had three different dandruff shampoos (with three different active ingredients) in the shower that I would switch between, if that tells you anything.
Also, I think that the different fatty acid profile of someone eating overwhelmingly Primal has a lot to do with this - my skin in general is much, much happier since I dropped the factory seed oils.
I have a mantra that I have spouted for years... "If I eat right, I feel right. If I feel right, I exercise right. If I exercise right, I think right. If I think right, I eat right..." Phil-SC