It's an interesting mechanic because it feels powerful, but it'd actually be extremely tame in Mage Wars. In your example, it results in 2 bonus damage, on an absolutely terrible roll. It reduces the psychological impact of rare dice catastrophes, but it doesn't actually change much in terms of attrition.
Tactically, it could be useful, though, because it would mean that a 6 die attack would be guaranteed to at least roll a couple of 1s, so there'd be less uncertainty in finishing off a badly wounded creature.
Oh, and it would hose Incorporeal, so probably don't do that.