[Fern]

 
Combination Fighter lowers Bellowing Stag's damage in spite of it not being a Soldier Offensive skill or a Demon Hunter Sword skill. To test, perform a Reaver Stance combo with Combination Fighter on and have enough momentum leftover to switch to Matador Stance then use Bellowing Stag. It will do far lower damage. I had a sword in my main hand when this happened to me, could it be that it's assuming it's a Sword skill because of that?