Anyone remember the conditions to complete this achievement? I did it on my ranger a long time ago and can't really remember how it was done now. I tried to get it on my new shadowknight last night, only using Ignite Blood since it's the best fire dot I have and got nothing. As I recall, mobs can be dpsed, but only if weapons don't have a non-fire proc on them. Doe the finishing blow have to be from a fire spell, most of the damage or some other specific condition?
Touch of the cursed innate procs will be problematic for Shadowknight melee. Search your logs from failed attempts for "You have failed to use fire on the heretic. The achievement 'Burn the Heretics' can not be completed." That should let you know what spell/proc is causing you problems.
I had not thought of that. My current setup doesn't have good access to fire spells, so it's a bit worrisome to me. I think the best I have is a level 60ish fire dot on the sk and burst of flame on the shaman.
I made an audio trigger for that tonight, it never went off and the achievement didn't unlock, so I'm assuming it's broken.