As far as I know neodymium is currently used for magnets in a lot of wind turbines and electric motors among other things. It's not rare but the vast majority of it comes from China right now. I can't speak to how much efficiency it adds.
It's completely possible that current windmill designs are only possible with neodymium magnets. We would need to ask turbine designer.
But it also seems to me this might be a cost issue... it's possible that neodymium magnets are used because they're cheaper in context than ceramic, alnico, or other materials. That could change if neodymium prices increase substantially due to scarcity.