Originally Posted by
Kevee
Yes, it is based on the stacks, but if your timing with Death Sentence is off the first Conflag won't have a fireball to go with it, hence it being a short one.
The reason there's long and short is that the conflag is constantly in flux looking at waxen flesh.
When you soak one in the hot tub, the debuff falls off and the Conflag adjusts to that. When you don't have one to soak, it's the 4 stack duration.
What this means is that at certain DPS thresholds the conflags will be opposite.
What you want to be looking for is the pattern of conflag/fireball each time, not "burn CDs on even."