[2019] Armour spikes currently do not work on large monsters unless you stand on the southwest corner of their model.

Originally posted by ItsLuckyDucky

The short of it - You must be adjacent to a large monsters southwest tile of their model for armour spikes to work.

On ripper demons, they are a 2x2 tile monster, you must stand adjacent to their southwest tile for the armour spikes to trigger. (Giving you two spots you can stand)

Vorago, is 5x5 (i think?), standing in the middle of his hitbox on the west or south side will not trigger them, if you move one tile closer to the southwest corner, they start working again. (Giving you four spots you can stand)