It's not a lot of work for the person registering, but it's a pain and an unnecessary hassle to have to wait a few days depending on the activity of the administrator to edit a wiki, especially a wiki that is not high traffic as you stated.
It is a lot of work for the administrator. It will quickly turn to a boring and repetitive task, with no real purpose. If they want to spend that time they might as well look for better ways to fix the spam detection or manually delete the spam accounts.
I still do not see the benefit of adding another layer of administration. Having the players re-register on different sites (forum, game, wiki) is onerous enough.
