It seems that the dual dagger power attack speed is unaffected by dual flurry... Is there a fix in a mod or console? Or is there a fix in the upcoming patch?

It depends on the Dagger being used. I can't remember which ones do not get the added speed, but equip two Elven Dagers and hold on.

The speed bonus is applied pending the left hand. (For ex) Put a dagger in your left and a mace in your right.

Oh! Where's my manners? Welcome to the forums and have a complementary fishy stick.

http://images.uesp.net/c/c4/Fishystick.jpg