However, in Modern, with the Tron lands able to produce tons of colorless mana quickly, this could be an option. There are plenty of Burn decks in Modern, and this can shut down anything that targets you, including discard spells like Thoughtseize and Inquisition of Kozilek.
The other plus to this card is that it reduces not only the damage of creatures dealing combat damage, but damage from their abilities as well (think Eidolon of the Great Revel). It also shuts down the Deceiver Exarch/Splinter Twin combo by making those infinite Exarchs deal 0 damage to you. This forces your opponent to use Pestermite, a much more fragile card, or Bounding Krasis, instead. This card also makes Lingering Souls pretty bad unless the 1/1 flyers get equipped..
Witchbane Orb has seen play in Legacy sideboards before. While this is one more mana, it may see play, perhaps in Legacy, but more likely in Standard and Modern.