When dual wielding, the Attacks Per Second displayed in the details pane does not match the Damage Per Second that is displayed.

The Attacks Per Second that is used to calculate the Damage Per Second while dual wielding is as follows:

APS = Attacks Per Second used to calculate Damage Per Second
APS1 = Attacks Per Second of weapon 1. Base value, NOT modified.
APSM = Attacks Per Second modifier
ASI = Attack speed percent increase

APS = (2 * [(APS1 * APS2)/(APS1 + APS2)] + APSM) * ASI.

The Attacks Per Second that is displayed in the details pane is APS + APSM, which includes APSM twice.