This has been adequately discussed. You also appear to have answered your own question.
So I've yet to really see any conclusive details in regards to the value of the tier 2 daggers, at least not that I could find.
According to Simcraft, my regular Nok + Vengeance is about 300 dps ahead of using both tier 2 daggers. Add a little extra for tier 2 off hand with current setup too. Is simcraft not accurate? Or will I still not be using both my daggers even with tier 2?