I lean towards roll one dice 1: squabble (can't do anything) 2-5 nothing, 6: normal move towards nearest visible enemy.
Don't roll for War machines, Black Orcs, and non O&G units, or units under 5 models.

6 is generally good (though could be disruptive and a pain for missile units), 1 is bad but not crippling. Both results disrupt an ordered battle line, which is the point I suppose?

Black Orc leaders grant a re-roll, but must accept the second result.