In the Underhul elites the arcane dagger proc helps survival by stunning mobs for potentially a long period of time. I'm not convinced that the new Flameforged blades are superior, unless someone shows me that the proc can cut down mobs in just a few hits (which I'm sure it can't), because if you can't kill them quick you will die quick from all the aggro you've just taken by dealing all that damage. The way I see it, those daggers can only be used in a party where the other party members help to stun the mobs. Not so easy to find a cooperative party that often though.