Personally, I don't see much use out of them outside of PvP medium-speed where it's optionally quinted and serves as an attacker/precog.
As for the speedbow, if you don't have Arsenics, at least keep two Fog Shields, remove two towers and add a Vampire Stiletto/Dagger. I'd skip the plague in favour of a Freeze or, if upped, a Shockwave. Dunno how useful that Discord is to you, but at least a weapon saves one Fog Shield from destruction.