It seems that Off-balance applied by Sweep does not reduce dodge/evasion to 0. Not sure if it's just sweep or if Pummel is the same.
Here is Carnifex with Off-balance applied by Sweep. In the combat log it is indicated that he evades some damage from a grenade explosion.
And to make sure that it's not some rounding error or whatever, I netted him and exploded again. He doesn't evade anything this time.