I was trying to figure out something about Demonology's execute phase and target switching - namely if you deliberately Shadow Bolt an add or something at <35% health that is in no way important (so the damage is essentially wasted) would it be worth it for the 10 seconds of Decimation proc. Using DPET's for my character given by SimCraft I found this:
Ignoring the possibility of a Molten Core proc
DPET Shadow Bolt * Y + Av. Damage of 1 Shadow Bolt = DPET Soul Fire * Y, where Y = arbitrary amount of time spent casting spell (with or without Decimation)
7688Y + 13656 = 13320Y
13656 = 5632Y
Y = 2.424
So if you can make use of the Decimation proc for > 2.424 seconds then it is worth it to do this, and given that Decimation is a 10 seconds buff this will almost always be the case. The main example of this I am thinking of is on Lich King you can SB the Shambling Horrors or Drudge Ghouls, which is definitely wasted damage, but it will increase you single-target DPS on the Lich King.
The other thing I wanted to consider was whether it is a DPS gain to hang on to the Molten Core buff and not consume it with Incinerate if you are about to enter execute phase and can use MC to benefit Soul Fire instead. If you assume MC doesn't proc again whilst you are holding on to the buff (which is definitely something to consider) then the maths boils down to:
In order for this to be a DPS gain
DPET of Molten Core Soul Fire - DPET Soul Fire > DPET Incinerate - DPET Shadow Bolt
Which unfortuantely I have no idea how to work this out with raid buffs and don't have the inclination to figure it out from the test dummies
. Simcraft GUI won't give an indication of the 2 DPET's of Soul Fire since it combines them into one value. I would be interested to see if anyone could come up with some solid numbers to support or deny this.