I agree that you should work your way up Affliction first.
Shadowburn is a great tool for certain PVP situations, and every once in a while works its way into PVE as well, but it is not going to increase your efficiency at all. As for Demonic Embrace, in my humble opinion it isn't worth the points until later in the game, where that 15% increased Stamina actually makes a big difference -- when you have like 60STA, adding 8 more isn't worth the trade you'd be making by taking points out of Affliction, especially for the SPI redux.
Id try something like
this out, where a 41-point base in Affliction is all you need. You're looking at 2/5 Suppression until you reach your Hitcap, then move those points into Drain Soul for the Agro Redux.
With 4 extra swing points you can modify the build to your needs. Big Raids get Malediction, Small Raids/Familiar 5-Mans/Heroics you can drop some points out of Embrace and work with Devastation and Destructive Reach (again for Agro Redux.) PVP, maybe you wanna pick up Improved Health Stone and CoA or Aftermath.
Past the skeletal structure of this Affliction build, it is really up to your playstyle and what you intend to do that will guide where you put your points.