In case anyone was curious, because I was.
Changing NOTHING but weapon damage and type.
535 unholy with 535 2-hander: 181k
535 unholy with 535 DW: 164k
535 unholy with 575 DW: 171k
535 unholy with 615 DW: 180.9k
535 unholy with 655 DW: 195k
So after both your DW weapons are about 85 ilevels higher than your 2-hander, DW unholy > 2-hand unholy. Barley.
To lower that ilevel, if you have a 450 quest 2-hander, it's SLIGHTLY worse than 2 535 heroic ToT weapons, and SLIGHTLY better than a pair of normal thunderforged 528 weapons.