A terrible example. He was in the presence of Nihilus. He affected those around him by draining them. It's never even mentioned if he was corrupted or did they just use the effect on him to portray the effect Nihilus had on him.
It's not a "terrible example". What does that even mean? It's made pretty explicit that the proximity of Nihilus' servants to him (like those on the Ravager's bridge for example) had that kind of effect. All living beings in the Empire are touched by the force, and just in case it slipped your mind, there are a lot of Sith that "non-Force sensitives" are constantly around.
I doubt the developers would make a completely new facemodel JUST for him that looked like dark side corruption but wasn't when they could just use the already available dark side corruption.
Why would they need a new face model? This doesn't make any sense, so I'm just gonna ignore it.