Even though you'd be increasing the likelihood of hitting the 8 swing cap per attack round, you'd have to deal with the additional delay from dual wielding, which would be counterproductive towards maximizing your attack speed.
DW'ing them is actually faster, you just get *** by the 8-hit per attack round cap. DW'ing them now will net in more overall attack rounds, but due to the hit cap, less total attacks. If there were no hit/round cap, then DW'ing them would also produce more total attacks.