Why would we trade two starting players and a prospect for a 30 something pitcher having a career season? I'm glad you are not the DBacks General Manager.
I actually think the Cubs would be the crazy ones. Young and Drew are crap who shouldn't be starting and Dempster has been good for awhile.
2008 2.96 ERA 17 Wins 33 Starts
2009 3.65 ERA 11 Wins 31 Starts
2010 3.85 ERA 15 Wins 34 Starts
2011 4.80 ERA 10 Wins 34 Starts- Down year
2012 2.25 ERA 5 WIns 16 Starts
Prior to that 2005 33 Saves, 2006 24 Saves and 2007 28 Saves
Also, from 2000-2002, 40 wins as a starter.