But Vorik was just an ensign. He was never shown to be high-up in engineering. In fact, it was explicitly noted that lieutenant Joe Carey was B'Elanna's immediate subordinate.
And I recall reading an interview with the actor who played Carey that he would have wanted more appearances. I don't think it was because he was too busy. It was odd they brought him back years later just to kill him. I guess they thought it would add emotional weight. But after such a long absence, most people probably didn't know he wasn't a one-time extra.
And yes, Chell did make a couple reappearances, but he looked like a completely different person. They really drastically changed his Bolian makeup.
TNG era generally cocked up the concept of the characters' ranks because non-coms rarely feature as characters. However, as an officer, Vorik would have been quite high up the command food chain. chief petty officers would have been far more experienced but he would have authority to order them about. Often in TNG there are too many 'chiefs' i.e. smokin hot young inexperienced ensigns and not enough 'indians' i.e. crewmen and experienced older non-coms like petty officers and chief petty officers.