My personal opinion is that no spec should have 1.4 speed weapons, and Combat shouldn't use a dagger at all. Assassination and Subtlety should dual wield 1.8 speed daggers, and Combat should dual wield 2.6 swords/axes/maces.
Blade flurry should be changed from a cleave to making our sinister strike attack with both weapons, enforcing the 2.6 offhand, much like raging blow for warrior's and Threat of Thassarian for Frost DKs.