Well, here's the thing, Dex, as I outlined in my previous post, does far more for you per attribute point than Int does. So it's really just a matter of scale whether it's your primary or secondary attribute. Either way, Dex is doing more for you for each point you spend than Int is. It's not like the benefits increase as you get higher values of attributes. It is a constant, uniform (essentially) gain of stats per attribute point.