I guess I'd say, if you want action, do the whole body in an action scene. Portraits are like still life - they're not supposed to be active. Anyway, I don't picture heros or villains going into battle looking like they're trying to bite each other.
I picture Inquisitors as being more sinister in a quiet, controlled way that makes you shudder when you look at them. I don't think they go into battle yelling and screaming; they just casually deal with the opponent while maintaining their composure. They're like Myrdraal, completely terrifying because of their enormous power which everyone knows is hidden beneath their calm exterior. I picture Inquisitors pretty much the way Inkthinker portrays them (replies #183, 238, 243, 244 in this thread).
Koloss, on the other hand, are more like Trollocs; they're savage beasts with low intelligence, a low degree of civilization, and very low controlability. They kill for the joy of killing with no planning or strategy or consideration of the consequences. You can draw their teeth all you want and I won't object.
Anyway, my opinion is by no means definitive, but there it is if you want it.