On the 2.5 answer requirement — there is no such requirement. If you are looking at the Area 51 stats, I would largely ignore that page in a "health report card" context. It's an old school, antiquated attempt to measure the performance of a site by the sum of its parts, but those one-size-fits-all stats weren't a terribly effective way to measure the overall health of every community. We're looking for about 150-200+ questions during the 3-week private beta. That's a much better indication of whether you're attracting enough users to become a public site
Robert does not mention the distribution of users who are asking those 200+ questions.
We of course want as much diversity as possible in the questions authors however I was wondering if there exists an actual metric that is observed by SE gods to measure this ? If so then how can we assess if we are doing ok with regard to authors diversity ?