Before you go needless Apple bashing (not that I really mind, just think if you're gonna have a go - get it right!) that Apple built this based on Microsoft's spec. Microsoft does more to degrade your Mac experience than anyone else, just look at Office 2011 (can't bring myself to mention 2008).
Out of interest I signed up for an Office365 account hosted by Microsoft and loaded it to ML 10.8, low and behold the server address was the same in both the internal and external fields - as you would expect for a hosted service?
So I pulled the auto-discovery XML for both the Microsoft hosted exchange and from my hosted exchange company and sent them to one of the tech guys from the hosting company. They are continuing to look at but he did said the results appeared to go against Microsoft best practice guidance - figure that!!!