im not entirely sure about magic damage vs physical damage, look at all casters and healers weapon damage compared to tanks and melee and ranged, when i think about it pld cure is still worse than a smns or blms(loved that flaw in 2.x it really drove me nuts to no end) so I think that drk was somehow bent against the laws of what normally happens much like how ninjutsu is (they call it a spell but its calculated as an ability but foes actially works on its dmg output)
I really wonder what the jp forums are debating or if theyre perfectly fine not debating this, i imagine they having some similar debates over this but i could be wrong