Step one of any plan should be to increase the number of users which can use tribe at the same time.. which at the moment I understand it only 700 people. For me, what is the point of marketing the site when the simultaneous users is limited to 700 ? In fact marketing it (externally) before that limitation is removed might do more harm than good.

We had a thriving community during the first few years, but that gold-rush era of tribe is long gone, and so are most of the people. Pretending we have enough "active moderators" to re-inhabit all of these dead tribes is ridiculous. There's just not enough people left on the site. Sometimes it feels like Detroit - a lot of abandoned buildings that need to be bulldozed.

You prune the dead branches off a tree so it be stronger and more beautiful, same for goes for this place. Take the dead tribes, sequester them to a "graveyard" or "archive" area. The tribes still show up on search, but they're labeled differently. If someone wants to bring the tribe back to life, then it comes back when people start posting.

Take the active tribes and highlight them, make them visible. Encourage people to use them so they'll become even more active. Put the time and energy into the parts that are living rather than try to bring the dead parts back to life.