Gained a few levels, took 10-15 runs to finally find one with Conviction, but I didn't mind. No fire immunes around and 3-4 packs every single run.
Since Conviction aura lvl is monster lvl/8, a level 60 Hephasto will have a lvl 7 conviction aura, popping -75% enemy defense and -60% resists (or -12% immunity break).
Doom knights have exactly 100% fire resist on nightmare, so with conviction and apocalypse I could reduce them down to 59%. It still took way more time than most mobs, but atleast they were always grouped tightly together, and generally slowly approaching to melee range, so no danger whatsoever.


