We can't use both at the same time, which is a shame or using one on left hand for one proc because with their speed u have to use it with a proper setup tactic or against a specific class to take advantage of their potential.
feedback: i used both of them from epic quest (less value) for 2 years now, they are strong if used when they have to be used, no more powerful than others available (sc/rvr/pve).
The mirror of these weap are still available on WH and was never accused of being overpowered also the WE weap doesn't have any strenght on it so to use them we lose %crit and str, the gain/lose is fair enough without having a condition of main hand only.
Suggestion, put back these two daggers usable in main/off hand
also Spite have a unique appearance, we can't use it on other daggers because of the condition of main hand only