I have to disagree on Neelix being more of an asset than Tuvok. Perhaps at various points, one was more essential than the other. But overall, they both made very important contributions to the ship. Certainly Neelix was more critical in the beginning, as a means of interacting with other species deep in the DQ and knowing important aspects of spacial regions (where to go, what to avoid, possible sources for supplies), in addition to food procurement and preparation.
I'm having a lapse in memory about Neelix though... wasn't there a point where food replicators were restored enough to significantly reduce the need for Neelix to cook? Memory Alpha details his role, but doesn't indicate anything about his workload over time.
One other thing about Tuvix, was that while he was permitted to mingle among the crew and assume some duties, he began to appreciate his particular combination of knowledge and skills. And interacting with the crew was a great satisfaction. It didn't take long before he realized what he had and then lost his nerve on letting it go. Of course, if they had put him in stasis, there wouldn't have been much of an episode... or there could have been another sub-plot, but then there wouldn't have been a contentious story provoking so many conversations about it many years after it was filmed. "Just another humdrum Voyager episode."