The Howl used by both the Shadow Mastiff summon and the druid wolf form appears to do nothing to hostile creatures.
Its an extremely low DC, and a pretty low range despite the graphic.
Area of effect: colossal
DC of 10 + a quarter the caster's hit dice (which is going to be 2 max)
For what it's worth, I know the druid form howl worked before but the howl that was on the animal companion never did. I'll check on the two you mentioned though.