It will probably be something simple like.
At level 10 +5 Dex given to your stats from your class will give 10% accuracy, but at level 50 it'll only give 2% bonus.
But then Equipment at high levels will always give the full 10%? but you'll never see equipment with +5 dex until the 50's etc.
Diminishing returns on Stats from character development.
Increasing returns from equipment development.