Q u o t e: if you just measured the time between when Diablo 3 was started, to when it is released, then no they are obviously not 80% done.
Actually, assuming the game is coming out in 2010 then they are currently approx. 80% done.
Sorry about the small nit pick, your post was otherwise perfect :)
Read the wiki and stay informed with Diablo 3 news.
http://www.diablowiki.net/Media_Coverage If it's already been explained we don't need another thread asking about it.