The range of the tether isn't very substantial in crucible for suppressing enemies, which is helped with either black hole or quiver. Quiver gives you the ability to get 3 kills which is much more useful than black hole, since most enemies don't conjure up close enough for the tether to be effective. Shadow shot isn't meant to be only a support class, as you can get kills with the actual super. It's primarily a support class, but in a game mode where the enemies are actually smart and can run from the tether, despite being slowed down, quiver actually gives you the chance to get the kill. I'm sorry for saying that quiver was the "only" viable option, I was just exaggerating it.