Abyss is never meant to be a sweeper. You can't compare Abyss to WoG just as you can't compare Humility to WoG. They serve different purposes with abyss/Humility requiring secondary cards to be fully effective (unlike Moat). It functions differently from WoG/Disk. It functions more closely to cards like Moat/Humility i.e. not a sweeper, but a staller. Moat is usually much stronger than Humility because against the right deck, it's an end to opponent's combat phase entirely. Humility/Abyss don't sweep, but tend to be paired up strongly with a secondary card (Humility with Factories/Elspeth/Decree of Justice, Abyss with Jace/pin-point removal).

Abyss is just not being played much at the moment. When it does pick up, I won't be surprised to see it overshoot $150 and reach Moat levels. The thing that's stopping Abyss from being popularly played is there hasn't been an upsurge of UBx based control decks outside of BUG control, which primarily win with Deed. If UWx and BUG control start shifting to UBx control lists, the Abyss is the most powerful tool you can use against aggro (when paired with pinpoint removal). Aggro decks cannot beat a sitting Abyss unless they are ages ahead (in this case Humility can't beat those decks either).