For the past week and a half, I've been running with a 432 green quest item as my offhand. I seriously can't get any decent weapons to drop. I have, however, had a couple of Gao's Keg Tappers to drop with no one in the party that could actually use them, so I went ahead and took them just in case.
Unfortunately, SimulationCraft can't import my character to do some actual numbers testing, so all I can go by are the numbers I see in my metes while beating up target dummies.
EDIT: Wrong weapon linked.
Using the 463 AGI weapon in my offhand, but keeping the 450 STR weapon in my mainhand, my DPS seems to be consistently higher with 3 minute long tests, even though my Attack Power, off-hand DPS, and damage stats all go down. Using both 463 AGI weapons is a noticeable DPS loss (unsurprisingly, but I figured I'd test it anyway). But even though we get almost nothing out of Agility, it still seems to be performing better than my old 432 green strength sword.
Should this be happening? Is the weapon a big enough upgrade to counter the strength loss? Or am I just getting lucky with crits? I know No'Kaled was BIS for Single Minded Fury at the ass-end of Dragon Soul, but I'm assuming that was mainly because of the proc.
You can probably (though I'm not a 100% sure on this) attribute your higher dps to the larger weapon damage on the off-hand weapon vs. your 432, as most of a warrior's attacks scale with weapon damage. I.E., your Raging Blow off-hand and your Wild Strikes are probably doing a larger portion of your damage with the higher ilvl weapon.
I'm using the Archy Agil Polearm on my DK for the only fact that every STR 2 hander that drops is taken by the dps. It was 2,500 dps higher than my ilevel 450 sword. Also it had more stam and the crit / mastery was better. I'll use it until I find a decent STR weap. But I don't see any problems in using weapons for dps if they are higher.