I was trying out the skill Magic Crasher with both a regular Rod and Doppel Doppel SoM. I was doing the same damage ranging from 300 ~ 600, with the exception of SoM stone cursing, which then I did 800 ~ 1000 because of it's fire property.
According to the MC description, it saids:
"You do an attack that calculates damage using your MATK instead of ATK, but is decreased using the enemy's DEF, not MDEF. This skill overall damage is affected by cards you have in your weapon, your weapon element (in this case being fire element), size and element of the target (which is earth when they get stoned) and it might miss depending on your DEX"
Does SoM truely ignores Demi-Human Def when Magic Crashing?