Don't kill/loot everything, kite enemies and head straight for the Elites/Bosses. Buy a super high damage weapon from the AH, throw a high-value Ruby into it, as well as into your Helm. Don't bother picking up any loot that isnt gold/rare/legendary.
It can be done in about 6-7 hours, and that's a moderate pace.
\m/ (O_o) \m/ Alan Wake is the best game you DIDN'T play in 2010. Please Sony, don't kill Heavy Rain!