I'm going to play Devil's Advocate in order for you to up your budget...
No one wants to pay a lot for a bike. However, you want a light bike that can ride well in road, rain, AND on gravel and you don't like aluminum and also steel rusts.....which leaves carbon and titanium.
Based on your requirements, I would suggest either a carbon or a titanium Cyclocross bike with disc brakes. If this is going to be your "last" bike and you sound like you know what you like and what you don't like, I think that you should raise your budget quite a bit so that you can get exactly what you want in your "last" bike.
2014 Liv Lust
2013 Specialized Fate Expert with carbon wheelset (sold)
2012 Specialized Amira Elite
2010 Santa Cruz Juliana with R kit and Crampon pedals (sold)
2011 Specialized Ariel Sport,suspension post,Serfas Rx Women's Microfiber saddle (sold)