I'd go with the Blackened Acyrlia Blade in the primary and Centil LS in the offhand. Here's how I figure it:
Primary hand damage is greater on the Blackened Acyrilia Blade. With haste, you have 14/18 ratio vs. 25/33. With 18 delay, you swing 33.3 times in a minute vs. 18 times with the Wurmslayer. Note, the damage below is the base weapon damage (works well for determining averages, sans strength modifiers)
14 (damage) x 33.3 = 466
25 (damage) x 18 = 450
Close... until you factor in your damage bonus. Now, factoring in your 3 point damage bonus, you get more damage from the Blackened Acyrilia Blade
3 (damage bonus) x 33.3 = 99.9
3 (damage bonus) x 18 = 54
Double attack should go off around half the time at 34/34 if your skill is capped. That damage bonus applies to every swing, which means perhaps another 25 points from the Wurmslayer, but around 50 points for the Blackened Acrylia Blade
As for your offhand, you should be getting successful dual-wields about 40% of the time if DW is capped.
With the Blackened in your offhand, you'll generate about 40% of 466 damage (186). With the Centi LS there, you'll generate about 40% of 364 (145). There is no damage bonus with your offhand, though, so this is a relatively small number. In other words, you loose about 40 points of offhand damage (perhaps a tad more with quad attacks, but those are pretty uncommon at 34th), but you'll be doing 60-70 more with your primary *before* you factor in Double attack, so the net advantage would be with the Blackened Acrylia Blade in the primary and a Centi LS in the offhand.
Now, if you have very high strength (200+), you'll see a big discrepancy between slow and fast weapons. You get a lot of extra damage per swing with 255 strength. As your damage bonus increases, it will also be very important to keep the fastest (provided the ratio is close) weapon in the primary hand. You an find your damage bonus on lucy.allakhazam.com