Part of what makes Heretic AP gain so silly is that they are the only class who, outside of active pacts, can even semi reliably achieve a top tier desecration result whilst not having a class specific buff. This probably means that they hit the 7AP result too often particularly given they already have one of the stronger AP regeneration skills in Sadistic Glee.
WM and Defiler both have a very strong long duration defensive result, DOs have poltergeists.
Trying to brainstorm what works as the strong case defile result for a heretic whilst feeling like a change instead of specifically a nerf.
Share one of the defensives with WM/Defiler, probably not that exciting but works.
Summon a Wheel of Injustice/Sinmaster, feels a bit odd with them not being a pet class but given I'm regularly hitting imps could be better (particularly given kills with a pet is one of the grail acquirement criteria and otherwise is mostly only available via Hashaa blasphemy).
Super charged angel hunter ping that gives actual locations to everyone in a larger radius, feels bad for a raid kill result (possibly could only trigger if there are not currently any non-allies present).
Activating Abiding Wickedness/Ultimate Wickedness for a timer (presumably 666 minutes), not as cool as the WM one but not a lot is going to top that.
False Grail, gives the grail buffs for a timer (presumably 666 minutes) possibly including access to the dark power and the ability to fill it.