Daggers can be used well. In comparison to other weapons, they surely do a little less damage, but make up for that with a slight faster hit (also see the character stats description under combat). You may find, that using daggers compared to the slightly shorter swords, such as short swords and sabres, they would do approximately about the same damage in the same time interval.
When talking about PvP: the use of daggers takes a different style, based on the speed of the dagger, named: the madman style by some duellers. The use of daggers in PvP to good success -in my opinion- takes a very experienced dueller, who knows what he/ she is doing, as other experienced may have the advantage to strike one hit and win with swords or axes. To succesfully use daggers in PvP, one must try and develop one's own stealthy ways as backstabbing, with use of the game's mechanics, as indeed: a skill like that is not implemented yet.
note: all info here is OOC, actual damage and speed not mentioned, cuz they are considered spoilers