I have no data but it appears that every version of PS needs more horsepower and this is the case for Adobe Camera Raw as well. Just more data to process. And this is not all of Adobe's making as every camera that comes out the manufacturer develops a new camera raw that is "better" as it has more options.
Yet what is different? I can hardly see any difference on the surface or the processing engine that would make *such* a dramatic slowdown. I don't need an Adobe apology - I need an Adobe solution.