I am always to busy infight to check boss timings. I just want a big thing to pop up to remind me to use infernal. So this Weakaura pops up ~65 seconds before boss is supposed to die. Im using code from Fojji (Time to kill - https://wago.io/2o0Pz_GWT) here so credit to him. Awesome job. I just copy and pasted his code and made it work for the infernal stuff.
This Weakaura only triggers in encounters for Affliction Warlocks (Haunt Talent must be selected) and bosslevel mobs.