Demon hunter crossbow and dagger?

Why 2 crossbows can be taken, a crossbow and a quiver, a dagger and a quiver, but a dagger and a crossbow are not taken??? Is this how it should be?

Because, if this was possible, pretty much every DH build would combine two pieces of the Shadow’s Mantle set into it for a 6000% weapon damage bonus multiplier.

This was briefly bugged, where it was actually possible to equip a 1-hand crossbow and a dagger, and was patched out for precisely this reason.