What should I do to be at least on equal terms with them as another melee (warrior, non-daggerspec) class?

If you don't lag them they quickly maledict you so you can't dodge and hit and most likely drop your weapon.

If you lag them they outtank (most of them dex-based + evade) you and outdamage you with concealed strikes.

Daggers are light so it's hard to make them them drop it.
They can initiate combat with strong skills as well.
Combine it with balance of the sisters legacy and mace or whip.

And being arguably the most versatile/fun to play/powerful melee combo they have cool utility skills like hurl throat.

Any advice welcome!