Lol no mdef does not affect FFS-type attacks. Pdef also does not reduce it and neither does DD. It is NOT a magic skill(How so? Well does magic attack scroll increase their damage? No. Does dark eyes increase it's damage? No again...) The skill was never intended to ignore DD as only penetrate and full blown attack are suppose to do this on dekans...Also magic guard(the ranger one) and lvl 6/7(I believe 7) stone skin also do not negate FFS type attacks. According to YNK(at the time) this skill does not have the coding for a proper type of attack resulting in it being essentially "pure" or "true" damage(still reduced by lvl reduction and heroic lvl differences).