The needs of the many outweigh the needs of the few.

Tuvix needs to continue existing.

Tuvok and Neelix need to exist again outweighing Tuvix's need

The crew needs to be saved from Neelix's cooking and general incompetence, which have proved to be a more consistent threat than the borg. Thus, Tuvok and Neelix's needs are outweighed.

Janeway needs Tuvok to be there to talk her out of doing impulsive things like starting wars, causing civilizations to fall, buttfucking the timeline, or murdering crew members. This effects whole worlds, so the needs of the crew are outweighed.

They once showed Neelix taking a bath, and there is a chance (however small) that he might do it again. The audience's need to not risk seeing that outweighs all the previous needs.