Here is an example (not enchanted

)
level 72 Barb (skils, WW 22, Mastery 22)
86% chance to hit hell bovine = Sigon helmet, boots + Angelic set
84% chance to hit hell bovine = 2 angelic rings + amu
82% chance to hit hell bovine = Sigon helmet, boots + single angelic ring
78% chance to hit hell bovine = single angelic ring
A difference of 6 to 8% hit chance in the same as minus 6 to 8% DPS. There are diminishing returns as you go more and more AR, but it scales quite beautifully. Is it much, is it little? You decide.
I'd like to see numbers from a high level barb, though.