One of the pitfalls of setting a Star Trek show away from home is that great difficulties result in exploring the full impact of any given story on a character. Most character building is based on character alone, but when that character is separated from most of what gives that character meaning, there is a necessary limiting effect.
What I mean to say here is the character of Tom Paris suffered the most from being adrift in the Delta Quadrant. The Maquis members of the crew had redemption arcs of their own, but Tom had a wider curve, since he was an outcast to both Maquis and Starfleet in the first episode. That he quickly proved his worth didn't mean that his inherent characters trait could easily be demonstrated later on, however. He was the outsider who could fit in, but was still an outsider. (And no wonder that he ended up married to B'Elanna Torres.)
In an episode like "Vis a Vis" (much like the misunderstood "Threshold"), Tom Paris undergoes one of his periodic lapses into antisocial behavior, grounded in his instincts that few are properly able to comprehend. When he alienates everyone, even tagalong buddy Harry Kim, there's no one to understand what he's really going through, no family or friends who knew what he was like before his life spiraled out of control. That's what's missing in most of his episodes. Robert Duncan McNeill seems to understand this in his acting most of the time, portraying Paris as someone who's tired of people not "getting" him, and sometimes simply doesn't care. He's got good instincts and bad instincts, and sometimes he's caught up in both of them.
"Vis a Vis" is a basic version of that character arc, which became harder to explore the longer the series continued.
Franchise * Series * Essential * Character
Memory Alpha summary.