I'm a fan of working right to shadow mastery. I pick up improved drain life because I find myself using that spell a lot to reduce downtime. Here are my talents at 39: http://db.vanillagaming.org/?talent#IA0i0RbkA
Then I start down Demonology for DS: http://db.vanillagaming.org/?talent#IA0i0RbkAZfxhzT0o
This is just my personal preference and I don't claim that it's numerically superior to other builds. I find that it really shines when I stack shadow damage gear and, of course, stamina.