If I use McMurrough's beserk attack in CC and also martial arts L3. Will my opponent get a -3 mod on their ARO, or does this only apply in F2F?
Opponent MOD: A MOD applied to the Attribute of an enemy when making a Face to Face Roll. It only applies to face to face rolls, so the Martial Arts level 3 option won't apply vs. berserk attack.
But you should still get the +3 to McMurder's CC from the other half of MA3, and the +6 from Berserk.