You have two possible routes, one is using all the bursty talents ( Surge of Darkness, Shadowy Insight, Clarity of Power ), and gearing either for Mastery/Haste ( great damage overall and easier to get off casts ) or Mastery/Crit ( RNGesus gearing ), second is using all the insane damage output talents ( Insanity, Power Infusion, Auspicious Spirits ), going Multi Dot mode and absolutely DESTROYING everyone with Orb procs and Insanity usage - gearing for Crit/Mastery obviously.
The problem with second option is that you are simply not allowed to cast right now. When I'll play my Rogue and any other class I have, I'll want to sit on a Shadow Priest that isn't using the first option purely because I shut him down so hard at this point of game ( although I suspect, in later seasons.. shit's going to be insane with the second option and potential DoT cleaves with Boomkins and/or Warlocks, etc ).
Idk is Shadowy Insight really worth taking over Power Infusion if you're going for burst windows? I suppose more Mind Blast procs means more windows of opportunity but I would think PI would be preferred for sealing the deal on a kill. Ill have to give SI a try.