For a few days i have been looking into issues regarding a build I’m trying to make around Infernal shade with the Devour in Flames node.
First off, the resistance penetration enemies are supposed to get with area level applies to minions.
Second, YOU get the penetration not just the enemies, thus Infernal shade actually deals more damage than it should (?) when cast on your own minions
Third, this can be bypassed by summoning minions in low level areas. Which means the enemies do not actually get penetration, the current resistance of minions gets reduced depending on the area in which you summon them. This persists even if you change into a higher level area/lower level area.
I tested this by summoning a bone golem with 50% fire resistance in a lvl 5 area. The damage he took was consisten trough all the areas where i took him. Untill i resummoned him in a lvl 40 area, then he got hit with the lvl 40 area resistance penalty and started taking more damage. Some of it might be intended, but no way builds with permanent minions should be summoning them in low level areas to avoid resistance penalties.