Diff in proc rate between 100dex-200dex?

[Pyrocat]

Actually now that I look at the code more, if 0 DEX = 0.5 proc rate and 255 DEX = 2.0 proc rate for main hand, shouldn't it be something like

PPM = (DEX/170) + 0.5

that way 0 DEX = 0.5 proc per minute and 255 DEX = (255/170) + .5 = 2.0 proc per minute