Im quite sure that build has been posted in this thread already.
You should drop 2 Points in Butcher to get Wrath of Xotli though.
The pulsing damage from your transformations is a huge part of your DPS (~8%). So 1 point in Wrath of Xotli equals 1.3% more damage which is a good investment regarding one talent point.
The same holds true for Burning Skull as you already stated. Improved Burning Skull parses for 2-3% of your overall damage, again for a mere 1 point.
Also imo being able to stun is enough and increasing the time of the stun is not essential so you can free up two points there, as Mana can be an issue frequently using Exultation, Root, Flame Lash (let alone riddle 6(?) at Zodiac) they could either go to Fury of Xotli (good one point wonder) and Hellfire Feast or plain to Xotlis Vengeance (for a tinsy bit more damage) or to Undying Glory if one tends to die a lot.
Putting it all together:
http://goo.gl/Nbd7D
But then again i prefer the Searing Hatred/Butcher Specc(possibly with Inferno Curse), but that's already been discussed in this post.