It's widely known that after a warlock who is speced Master Demonologist and Demon Sacrifice can ressurect their pet after they sacrifice it to get both bonuses. For instance if you sacrifice your Succubus and have it resurrected (really quick) then you get 15% more shadow damage and 10% more damage.
What some people don't know is you can Soulstone your Succubus so you don't need to have a Priest handy to get 35% more damage to all shadow spells.
Turns out this is false. Sorry for the error.
But, you can have an enginner use goblin jumper cables on your Succubus, but it only works 50% of the time.
You can also respec while you have this Sacrifice/Resurrect bug on, and you could respec to Shadow Mastery/Ruin, and you keep the Master Demonologist aura and Demon Sacrifice buff untill you logout or die.
So in theory...
10% from having a Succubus out
15% for sacrificing her
10% from Shadow Mastery
Thats 45% more damage base. You could also do these for even more damage:
30% more damage "Bezerker" buff from battlegrounds
20% more spell damage from a Priest's "Unstable Power"
200 more spell damage from a Flask of Supreme Power (About 175 more damage to Shadow Bolts, and 200 more to total DOT damage)
10% more shadow damage from Curse of Shadow
15% more shadow damage from Shadow Vunurability
This isn't a joke, either. With ALL these buffs on your Shadow Bolts would HIT for about 2500, and CRIT for almost 6k. With just the first 3 and a flask of supreme power, you would be hitting for about 1700 and crit for around 4000.
Enjoy
~Sym